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MISCELLANEOUS TIPS: Some typing errors are a result of converting an email document into a plain text document


Engine/Prop shaft alignment, cutlass bearings

Carberator & fuel problems

Cooling system problems, thermostates, overheating

Cooling system acid flush

Engine Design

Blown Head Gaskets (See also Cooling System)

Muffler Types, Configuration

Oil, Filters and Changing methods

Treating Rust spots and Painting Engines


Replacement of Engine

Engine & Prop Size, Speed, Tachometers

Transmission & Clutch Adjustment

Troubleshooting your engine

Tuneup Tips

Valves and Adjustments

In the Atomic-4 Caster Newsletter 21, Oct. 96, Don Moyer, the A4 guru wrote:

Buying a used engine: IN terms of price there is a sort of threshold between engines which are considered inoperable and those that are reported to be in "good running condition" and could conceivably be used as a replacement engine. That price threshold for the first catagory is about $1,000, and depending on the degree of overhaul that may be claimed, the asking price of an operating engine could be as high as $2,000. For Non-running "parts" engines, I usually offer no more than $250 and the main issue in this case would be the condition of water-jacketed castings." (Block and Exhaust manifold).


Joe Zajac wrote P-28'ers, I just did this alignment job on my '76 P-28. And have the following tips ...

Shaft Removal: Keep the engine from turning by using a hand crank or blocking the prop with a 2 x 4. Remove the set screw holding the shaft in the coupling and then remove the 3 (?) bolts holding the coupling to the engine. Clean the shaft of bottom paint then using a small hammer and a wood block, bang the coupling off the shaft. Pull the shaft out.

Cutlass Bearing Removal: Capt'n Ron pointed out that the bearing can only come out the aft end of the strut since there is a lip at the forward end. Do not bang on the strut to get the bearing out. This will certainly break the seal to the hull. I decided to remove the strut and rebed it with new silicon bronze bolts. Calders book has a neat bearing removal tool using threaded rod. I've also heard of people hiring the boat yard's hydraulic press for this. I had to use a hacksaw and cut mine out. :)

Shaft: Back in the 70's stainless was expensive so we all got the bronze shafts. My cutlass bearing was so worn that the shaft was flexing in the center and actually hitting the hull in the stern tube! The vibration was not too bad and if I had let this go it would have sunk the boat by wearing a hole in the fiberglass! I replaced the shaft with Aquamet-22 from Have the shaft coupling fit to the shaft by a machine shop so you know that the shaft and coupling face are perpendicular. Again

Prop: Had the prop reconditioned

Stuffing Box: Replace the stuffing box hose with proper "stuffing box hose" available through a propeller shop. Do not use exhaust hose. New hose clamps and new flax in the packing gland.

Alignment: Support the shaft in the center of the stuffing box. Then move the engine until the two faces of the coupling are parallel. That's the key, the two faces only need to be parallel.

My engine is now smooth as silk!

Good luck its a big job to do it right. Joe Zajac

Atomic 4 Engine Alignment Louis Mihopoulos (CptinHook), asked:

(( My thoughts on the transient vibration I noticed toward the end of the season were confirmed. The cutlass bearing has worn out. I was wondering if you've had any similar experience with "Mystic". I am planning on replacing the bearing myself and was wondering if you had any information that may be useful to me. Specifically engine-shaft alignment, and removal of the old bearing. I also have a copy of Nigel Calder's book. I am new to inboard propulsion maintenance, (my first boat was a Kells 23 with an outboard) but a pretty good mechanic. ))

Yes, I had a similar experience, except "Mystic" had no noticable vibration until after I had replaced the cutlass bearing. It had worn irregularly but somehow remained aligned with the engine. Essentially it appears to have worn as the engine mounting gradually vibrated out of alignment. I had to realign it after replacing the cutlass bearing, the vibration was so bad it sounded like something was thumping against the hull.

You might as well plan on replacing the packing material in the packing gland when you replace the cutlass bearing. On my P28 the cutlass bearing was set into a recess in the propeller strut, there are sholders fon the forward end of the recess that prevent the cutlass bearing from sliding forward, it will only go in and out from aft. There is an Allen wrench set screw on one side of the cutlass bearing, I don't believe there is one on each side. After removing the propeller and shaft, and the set screw, the cutlass bearing slide out with very little effort. Sometimes they fit so tight you have to cut/chistle them out. Hopefully you will not have that problem.

Nigel Calder's book cover's the basics on alignment, so does Dan Casey's "This Old Boat". What neither of them address is how to adjust the alignment when you don't have adjustable engine mounts. The basics are the same, what it really amounts to is biting the bullet and getting down there in that uncomfortable cramped engine compartment and doing it. Its harder on the Atomic Four because it wasn't installed with the adjustable mounts, but its not rocket science. You have to get in there with pry bars and try to shift that 500 # hunk of metal around a few thousands of an inch at a time until you get the faces of the coupling aligned, it requires perseverance. And a tolerance for being uncomfortable while doing it. Remove every piece of cabinetry and boat parts that you can while doing this job (even the sink cabinet if its in front of the engine as mine is), you need every bit of clearance you can get to do this job. Also knee pads or boat cushions to kneel on help.

A contractor's wrecking bar can be useful, its essentially a thin prybar made of flat metal. I found it can be helpful to have an automobile scissors jack to move the engine small amounts. I put a short 2x4 along the fiberglass or wood sides of the engine compartment to spread out the load and give the jack something to press against. A small sledge hammer can be helpfull too, but use it to gently tap on the appropriate engine mount to encourage it to move small amounts.

More than likely your engine has settled from vibration over the years. Since the engine supports slope down hill aft, the motor probably moved that direction, so a good start is to move it up hill, away from the coupling. But check your clearances first.

I used S/S fender washers to adjust the hieght of the various motor mounts until I got it pretty close. I didn't have any shims, apparantly someone makes shims in different thiknesses for just this purpose, I haven't yet figured out where to purchase any. I could see where one or two had split and worked loose from my engine mounts.

Was able to get mine adjusted to where the vibration was greatly reduced, but I think I still have a little bit, it still seems more than what I had before. So I expect to make another stab at it some day, after I find a source for the shims. I have not asked Featherman if he sells them, he can probably get them.

I hope this is helpful, you may have already seen the postings below, they are part of the "A4tips.txt" document that is posted on my web page, but I'm including it incase you missed it before. Let me know how it turns out and if you have any tips to share with other A4 owners, I'll add them to my web page. Fair Winds, Ron

Atomic 4 Engine Alignment QUESTION FROM CPTNRN:

((On my 1975 Pearson 28, with an Atomic 4 engine, I replaced the cutlas bearing last month and now have a bad knock at higher engine rpm's. The cutlas bearing was worn unevenly, indicating prop shaft alignment problems, the shaft looked straight eyeballing down its length. I assume the engine has shifted over its 20 years in place and needs to be realigned with the shaft. I've read about how to do this but all the manuals assume the engine will have adjustable engine mounts. This atomic 4 is just bolted to a sloping fiberglass housing that supports the engine on both sides. Does anyone have any tips on how to align this? ))

RESPONSE From: Wally Kowal ( This is one of the next jobs on my "to do" list {Why do these things never get shorter? ;)} I have the same engine and installation and was told to use washers under the mounts to raise the engine. Because of settling over the years, it's unlikely that you would have to lower the engine, but if you did you would have to shave off some of the supporting struts. This would entail raising the engine and going at the strut with a file. Don't forget that the engine has to be aligned in three dimensions so that it sits perfectly in line with the axis of the prop shaft as well as up/down and left/right. Most likely you will only have to raise one end of the engine to get your alignment, but I have been warned that it can get terribly finicky. I don't relish spending a few hours under my cockpit sole bent over double (I'm *way* to big to fit but manage it anyways).

You have to support the prop shaft end after removing the nipple from the engine. Press the nipple against the engine (transmission, actually) and move a piece of paper around the interface of the nipple and engine. If the paper moves freely at the bottom but not the top, raise the back of the engine. If the paper binds at starbord, rotate the back of the engine to starbord. Most experts recommend using a feeler guage rather than a piece of paper, with the gap being no more than .001 inch for each inch in diameter of the coupling. i.e a .003 inch gap on a 3 inch coupling is fine.

If you have it aligned and you still get knocking, it's likely that the engine is not aligned along the axis of the prop shaft. You would then have to move the entire engine, up, down, left or right. Frankly, other than trial and error (and maybe a good eye), I have no idea how to measure if the engine and prop shaft are aligned around the same axis. Perhaps someone else has an idea for this. As you're down there sweating away, just remember that you aren't alone. Packing Gland Flax Replacement: I just replaced the flax packing in my stuffing box (P28) and used 3/16" packing. I chose not to use the dripless kind because it can overheat the stuffing box if it is compressed too much. I removed three pieces of the old packing but was able to fit four back in when I reassembled the box. So far the box seems to run cool enough but I am getting less than the three drops a minute reccommended to ensure lubrication of the stuffing box, even though the nut is only hand tight. I haven't replaced the packing in the water but thought if I had to I would find a peice of 7/8" steel rod and pre cut the packing to the correct size ahead of time. The packing rings in my boat go in the nut so I would just slide the nut up the shaft and let the box leak while I replaced the seals.



Subject: Re: Carburetor adjustment Date: 25 Sep 1997 18:32:05 EDT From: Qshicks

thair is 2 adjustment on late model one is a air /ideal seting that is on the buterfly and you should not have touched it the other is the ideal /slow speed neadel valve and the seting for that is 1 1/2 turns from closed and then lean from thair most moters run well with the valve set at 1 1/4 turns open the high speed jet is fixed the moter should idel out of gear at 700 to 800 rpm with the chock off and the moter warm

Carberator float dimensions: I had two different dimensions for the float level adjustment. The one that seems to have come with my Atomic Four owners manual made no sense. However, the numbers I got in the instructions for the kit from Don Moyer 1.25-1.31" (top of housing to top of float) made complete sense and I adjusted the floats to these specs and they were perfectly level. (Which is the goal when the upper carb housing is held with the floats facing upward).

From: "Hess" To: Subject: Re: NO CLIP Re: carborator problems please!!

About half the Atomic Four carbs I rebuild have a clip for the needle and seat. The latest kit sold by NAPA doesn't include a clip, but the older kits did. The clip positively pulls the needle down when the float drops in case it sticks in the seat, however modern gasoline doesn't gum up and make the needle stick like the old stuff did, so the clip isn't really necessary any more. Robert

-----Original Message----- >From: >To: >Date: June 5, 1999 4:51 PM >Subject: NO CLIP Re: carborator problems please!!

>I just took apart my old A4 carb, that I had brought home to rebuild, there >is no clip on it. The carb that is on my boat now is a spare that a friend >gave me, no clip on it either. Nor is there a clip in the overhaul kits that >I bought. 1 came from Don Moyer and 1 came directly from Westerbeke. Nor is >there a clip mentioned, or shown in the overhaul kits instructions, Don >Moyer's instructions manual, nor the Owner's manual. I haven't checked the >maintenance manual published by Seacraft yet, its on my boat. But I'm >convinced that if your carberator came with a clip connected to the needle >valve, that it must be some kind of rare device that was used on only a few >carberators. > >Fair Winds, Ron > > > >>To: >>From: Davew >>Subject: Re: carborator problems please!! >> >>Take your carb apart again and check for a clip htat connects from the >>float to the needle valve. If it is not there, that is why your engine >>stalls.The needle valve sticks. A rebuild kit is 25 just for one loosy >>clip, but mine did somehting similar. hope this helps >> >>Dave >

CANADA - Robert Hess. Sells rebuilt engines, parts and accessories Atomic Four Engine Service, 5017 Mariner Place, Delta, BC, V4K 4J4, Canada Telephone: 604 (868-6646) email:

This web site has an excellent history of the Universal Motor Company and the design of the Atomic Four engine. I thouroughly enjoyed reading the information provided there. Robert Hess also provided some information that seems so important to Atomic Four owner's that I'm reproducing it here. His business is rebuilding these engines so I think it is prudent to listen closely to what he has to say. It has inspired me to go out and buy a timing light.

etting the ignition timing by adjusting the distributor while the boat is under full power ("power-timing") can sometimes result in excessive ignition advance, which can contribute to head gasket failure (or worse). Pre-ignition and detonation (knocking) caused by excessive ignition advance or high compression can cause head gasket failure, cylinder head combustion chamber damage, piston crown collapse, piston compression ring and ring land breakage, valve face failure, and connecting rod bearing damage. Poor grades of gasoline (usually found in third-world countries) with octane ratings below 89 make lowering the compression ratio through the use of two gaskets more important in order to reduce head gasket failure or other damage. Although leaded fuel was originally designed to reduce engine valve seat failure as well as raise gasoline octane rating, especially in engines such as the Atomic Four which do not use hardened (Stellite) valve seat inserts, the use of unleaded gasoline in the Atomic Four does not normally cause any damage to valve seats as long as the valve clearance is properly adjusted and stock valve springs are fitted. For that reason it is considered more beneficial to add octane booster when the fuel octane rating is below 92 than it is to add a lead additive to unleaded fuel.)) From: "Paulus, Jon" " Earlier this summer I posted a note to the a-4 list about a fuel filter I'm using that fits in the sediment bowl of the fuel pump. I finally got around to digging in my spare parts bin and found the number: It is from Big A auto parts; two part numbers: 33034 and (in parentheses) 95034. The Big A auto parts guy in Vermilion OH, Fulper Auto Parts, stocks them along with the funny points cap condenser and rotor I have on my 67. I assume others can order them, tho I don't know how widespread Big A is. Back to the filter; it fits over the small barb on the center of the fuel pump casting. I've been putting the filter on first, then the gasket to hold it more securely in place, then the bowl. It's easier to do than explain..... maybe this will also help some other's fuel problems....

From: Larry Helber RE: fuel filter What have you been getting?

From: Paulus, Jon mine has a cylindrical filter in the fuel pump sediment bowl, been buying them for years at an auto parts store.

From: Larry As far as I have been able to find out that is actually just a sediment bowl. No filter goes in there and no one has been able to locate one for me.

> When I launched my new to me '78 C-30 yesterday I had lots of trouble > starting the engine. Problem was no fuel delivery. Long story short when > opening the fuel bowl I did not find a filter in it. Should there be a > filter or screen and where could I buy one (also might need to replacf the > thermostat gasket) . BTW., it runs fine now after got rid of some sort of > block in the fuel line.



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A4 engines normal operating temperatures.

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NORMAL OPERATING TEMPERATURES:The assumption that A4's with raw water cooling thermostates rated at 140F will run at close to that temperature is apparantly a fallacy. According to Don Moyer's description in chapter two of his manual, the normal operating temperatures vary as follows:

The thermostats are rated at 140 & 180 degrees (raw water & fresh water) respectively. The normal engine operation temperatures are as follows: When the engine is cold the (2 stage) thermostat blocks the water circulation exit from the block, forcing it to circulate thru the by-pass hose. As the engine approaches 140 degrees the t-stat starts to open allowing water to circulate thru the block...

"In the case of engines with clean water jackets (and no other problems) the temperature will tend to be maintained between 150 and 160 degrees"

"As the Engine becomes hotter...In a normal aging process, water jackets tend to fill with salt precipitate or sediment until it is eventually easier for water to by-pass around the block than to go thruough it. At this point the temperatures will tend to maintain between 160-180 degrees"

"And Still Hotter!...If the condition of any part of the cooling system is allowed to deteriorate further engine temperature will continue to rise."

"At about 180 degrees (!!!) the thermostate will be fully open and its moveable core will have reached the inlet port on the underside of the top of the t-stat housing through wich the by-passing water has been entering. (Maximum cooling).

"When ever the temperature climbs over 180 degrees, it is a clear indication of a malfunction..."

The overheating alarm is triggered at 200 degrees.

Salt deposites aside, the engine runs more efficiently at around 180 degrees, cooling it down to 150 with a 140 degree t-stat is the most the designers considered prudent to do. Clearly there is going to be some salt percipitating out and scale forming during the normal operation of a raw water cooled engine. That explains why Don Moyer recommends periodic cleaning of the A4 cooling system AND an acidic flush every 3-5 years.

I find a note of comfort here as an owner of a raw water cooled engine, if your engine starts overheating, anything below 200 degrees (for short periods of time) isn't doing any real serious damage beyond making more salts accumulate in the cooling passages. And they can be cleaned out.

Not that I recommend operating at these temperatures, but there have been times when the engine started overheating (impeller failed) as we were coming into the jetties with the wind on our nose, and I had to continue motoring until we could get into a more open area where I could use the sails.

The above information is why on my Atomic Four web page I list the normal operating temperatures as follows: 150-165 degrees w/ raw water cooling. 180-190 degrees w/ fresh water cooling.

NOTE: I see by the clarifications below that being in fresh water doesn't mean your cooling system will not accumulate scale in the cooling system. My boat was in fresh water from 1975 to 1995, the water around here, Austin, Texas, has such a high lime content from the surrounding limestone that even drinking water pipes clog up with lime deposites after 20 years or so. The A4 engine does not currently have overheating problems but I haven't tried to take it apart and see how much scale has built up. So I'm not sure of the effect in fresh water. That said, I have to admit that most everything else about maintaining a boat in saltwater is much worse.

David Evans wrote: )This has clarified something that has bugged me for a long time. I )wondered, "why should highly soluble SALT be precipitated out of )solution at 160F and coat an engine's cooling passages?" And why should )ACID (which doesn't react with salt) remove it? The answer, which I have )confirmed with a marine chemist, is that it's the CARBONATES that )precipitate out, carbonates being present in sea water (and in fact an )important part of the carbon cycle), and, of course, they DO react with )acid. Thanks for starting a train of thought which solve a puzzle. I )turns out that bicarbonates (like baking soda) unlike almost every other )water-soluble compound, decrease in solubility as the temperature rises )- and it also turns out that if this didn't happen, there would be )serious consequences for life in the oceans! )

)Remember everyone: it's not the salt that clogs things up, it's baking )soda! David Evans )

)RBHartt wrote: )) )) You won't clog it with salt, but you'll need to be concerned with )) clogging it with calcium carbonate scale. Ontario waters have about 130 )) parts per million of hardness and about 100 parts of alkalinity )) (carbonate and bicarbonate). At a bulk temp of 160, the surface temp )) will be high enough to precipitate this scale on the heat transfer )) surfaces. Higher the temp, the more likely to form scale. The scale )) will come off with an acid cleaning, but the lower temp will reduce the )) scale formation in the first place. )) )) Rich

Jerad wrote: )(( 150-165 degrees w/raw water cooling.)) ) )The magic number would vary: At 160F salt water starts leaving massive )salt deposits in cooling passages, doesn't it?

Jerad, I used to think that was the case. Actually I heard that its around 150 degrees where the salt starts to parcipitate out and it gets worse as the temperature goes up. I'm no longer certain of this, recent postings have indicated that its not salts but carbonate and bicarbonate mineral scale that builds up on the walls.

Water Pumps: Don Moyer suggested DEPCO pump Co in Clearwater FL at 1-800-445-1656. They have a great free catalog, knowledgeable people to talk to and will ship on a credit card. I paid $118.00 for a brand new unit, their model 202M-7 which is an Oberdorfer unit. They also carry two competing lines. Rebuild kits cost about $20 for the impeller, two seals and the gasket which is not quite half what I paid for the individual pieces at my friendly local boatyard. over haul pump including replacing the shaft or if to badly worn replace with anew obendorfer m 202pump.

Thermostates:(( On the weekend my engine overheated, and I believe that my thermostat has seized shut. I have just put a new impeller in the water pump, but no coolant water is making it through the engine. ))

Attached is one page of the manual which has a very small discussion of the cooling system and a diagram of water flow. Even with the thermostat closed you should be getting significant cooling water coming thru the engine and out the muffler. Cooling water to the block enters at the first hose connection after the pump below the alternator. It exits the block at the thermostat, which controls the temperature by open/closing that exit. A study flow of cooling water runs from the pump thru the hose connection at the thermostat to the hose to the exhaust manifold, and out he manifold to the muffler. Water should always be running out this line. Pull the coolant hose off of the top rear of the exhaust manifold and see if you have any water coming out there. The thermostat only regulates the water going thru the head, there should always be water going thru the exhaust manifold, if there is not then it or something downstream is blocked. It could be just a hose is blocked, perhaps by a piece of broken impeller, or you could have rust scaling and salt accumulated in the cooling system. the acid flush described below will clear that out.

Theron, you wrote: ((Re: Impeller blade missing somewhere!))

Were there broken blades missing when you removed the old impeller? If so check carefully the elbow fitting where the water exits the water pump. I've often found pieces there (also the intake fitting). It they are small enough to get past that elbow fitting they could have gotten into the cooling hose. Try back flushing the hose with water under pressure from the thermostate hose towards the pump, with the water pump impeller cover opened up and you may be able to flush the blade out.

(( I have replaced the impeller on my Atomic 4 and checked the hoses from the through hole to the sea strainer, from there to the water pump, and from the water pump to the block and thermostat. All seems clear! ))

If the pump is pumping water to the engine and you are not getting any water out of the exhaust you have a blockage somewhere. Try disconnecting the hoses at the thermostat housing and see if water is getting that far. If it is then disconnect the one at the back of the exhaust manifold and see if you are getting water that far. If not it will help you figure out where the blockage is located. You may just have a clogged up cooling jacket that could be cleared up with a mild acid flush. Raw water cooling engines in salt water are especially prone to mineral and salt accumulations in the cooling jackets.

Can you blow thru the cooling hoses or squirt water thru them using a hose & nozzle? If the hoses 7 fittings are all clear than that leaves only the thermostat or cooling water jackets. What kind of condition is the thermostat in? If both of its two valves are stuck it could be blocking the water path. If you remove the thermostat and replace the housing, water should circulate freely thru the engine unless you have blocked hoses or cooling jackets.

((However, when I try to run the engine it sends air out the throughhole and nothing out the exhaust system!! ))

I assume you mean "Through Hull". That is very odd if you are getting air out of the thru-hull. Could it be steam? Or combustion gas (hope not)? If you are getting a little water into the head, and the cooling water discharge route is blocked by mineral or salt deposites, the heat could turn it into steam which is very powerful and has to go somewhere, so it could be blowing out the thru hull. Be carefull, if you do this much you could damage the engine from overheating or from the explosive forces of steam expanding. Try disconnecting the water intake hose from your through hull intake valve and put it in a bucket of water. Then start the engine and see if your pump is sucking in water or blowing air/steam. You'll need a hose handy to refill the bucket.

(( I forgot to open the throughhole valve for about five minutes and this has caused the above phenomenon to occur. Do you have any experience with this particular problem?))

Running the pump dry does cause impellers to break up. I suppose of your engine overheated dry it could have caused mineral/salt deposites to break/flake loose and clog the cooling water circulation path or discharge pipe. There are lots of tips about correcting this in the document referenced above. Fair Winds, Ron

Subj: Regarding: Atomic 4 overheating Date: 96-04-2 7 11:27:07 From: LRZeitlin

I cleaned ten years of scale out of an overheating sea water cooled Volvo MB10 by circulating an oxalic acid solution through the water passages using an external impeller pump. I removed the thermostat and pumped the solution in the seawater intake, bypassing the engine raw water pump. The solution came out of the block at the connection to the exhaust pipe into a 5 gallon collection tank, then was recirculated by the external Water Puppy pump. After 2 hours, I flushed the system with fresh water, neutralized any residual acid with baking powder solution, then a final fresh water flush. I don't know how this would work on an Atomic 4, but the Volvo hasn't raised a fever since its enema.


Subj: freshwater A-4?Da te: 96-05-19 13:57:48 From: MCPapa58 I've been told that at one time you could buy a freshwater cooling kit for the A-4. My mechanic says he can build one from scratch for about $600. Does anyone know anything about this? Would it be worth converting my raw water cooled A-4 when it comes time to rebuild? Does anyone know where any of these "kits" can be had?


Subj: Regarding: freshwater A-4?Date: 96-05-19 17:44:01 From: LRZeitlin

It can be done but why bother? Clean the A4 out every other year using the process described in my post of 96-04-27 (see below). The engine will last another 20 years. If you choose to convert to fresh water cooling you will have to add a heat exchanger and an additional circulating pump. Basically, the approach is to convert the raw water system to a closed cycle fresh water system diverting the flow through a heat exchanger. Then you will need an additional pump to circulate raw water through the exchanger and to provide water for exhaust cooling. If you use keel cooling, you can omit the heat exchanger but you will still need to cool the exhaust. If you use a dry exhaust system, the process is simpler.


Subj: Regarding: freshwater A-4?Date: - 96-05-19 21:12:19 From: T27boat

I suspect you'll find this a worthwhile venture if you plan to keep the boat for any length of time. I've just done this with mine as I had then engine out for the Winter. I couldn't believe the accumulated crud inside the jacket. Mine is sailed in salt water and is a '74 model. I found little evidence of serious corrosion and am now much more confident in the state of the engine. I bought a fresh water cooling kit from Don Moyer at Moyer Marine, (717)564- 5748. Don has been selling these "SENDURE" kits complete for $450 although he has had to raise his price by about $50 since the past holidays in response to a cost increase to him. The kit is well thought out and installs easily, but I would recommend waiting until the engine is out so you can go right thorough it in terms of cleaning it out and fixing the little things you'll find need attention. I hand lapped the valves, replaced the transmission output shaft seal which was leaking a bit and generally cleaned all threaded holes and replaced corroded bolts. Not brain surgery but it was kind of fun. Certainly periodic cleaning out of the chambers will keep the system clean and more effective over time, but, and this is a big but, salt water WILL eat cast iron over time. Periodic cleaning can't stop nature where FWC can. You can buy everything for an A4 except a new block and once your block thins out too much to hold it's studs, bolts and cylinder walls in place you're all done. Good Luck, Bill

Subj: Regarding: freshwater A-4?Date: 96-05-30 01:27:44 From: Capt Olaf I guess the real choice between periodic cleaning and freshwater cooling depends on how long you want to keep the engine. Raw sea water is harder on the block than fresh water, however many of the local fishermen around my area have been running Universal Twins, A4s, and small Volvos for three to four decades with raw water cooling. They flush the blocks periodically with freshwater and always flush before winter lay-up. The simplicity of raw water cooling has much to recommend it. I figure that by tie time a motor has given me 30 years service, it has paid for itself and I can afford to retire it.


Subj: Regarding: freshwater A-4?Date: 96-06-19 16:59:57 From: GLelievre It is absolutely true that you cannot reverse the effects of nature. Everyone knows that saltwater makes excessive rust on cast iron. Spend the money on fresh-water cooling. I've seen many an engine go because of the salt. My A-4 is 31 years old (soverel 28') and fresh water cooled. A little Mystery oil in the fuel, and she'll run indefinitely. On another note, I also heard that CDI has a plastic prop for Direct drive A-4's that increases thrust in reverse. Anyone try it? "Apocalypso" Soverel 28'

Subj: Regarding: Atomic 4 overheating Date: 96-0 6-25 10:02:22 From: Whk4676 My raw water cooled A4 is also doing the same thing--it's gradually climbed to 200 degrees over the last year. I'm getting pretty nervous. The water flow seems restricted: less and less water is coming out the exhaust pipe. We removed the thermostat and nothing improved. Impeller is OK. There was a considerable amount of black, greasy gunk in the thermostat housing area, however, which wasn't there the last time I checked the 'stat a few years ago. The engine itself is circa 1967. Any ideas? Reply if convenient to, as this is my Dad's account. Thanks in advance.

Subj: Regarding: Atomic 4 overheating Date: 96-07-02 18:10:28 From: JLantz2910 I had an overheat problem and it turned out to be the thermostat housing cover that allowed the water to bypass the block. New cover solved the problem and it now runs about 155.Jlantz 2910

Subj: Thermostat Date: 97-01-04 17:55:39 From: DJandon Has anyone replaced the thermostat and if so with what model # and from who ?BOAT/US has one listed for $91 .00 .I think "Don Moyer ?" from Harrisburg has one for around $30.00. Is there a cheaper alternative ? I mostly sail in the upper Chesapeake Bay area. Salt water wouldn't be a problem. But I don't care to run the engine without it. Thanks for any info.. Dan

Subj: Regarding: Thermostat Date: 97-01-04 22:09:54 From: Qshicks - do not run engine with out thermostat cooling system is a by pass system on all post 1969 motors and you run risk of damage from overheating and the temp gauge will hardly show any heat but block will over heat I have bin a universal dealer for 30 years and have seen several damaged blocks i don't know of any source for tstat except universal try your dealer if he cant help i stock them you can clean them and restore proper operation by socking in acid (muratic )get at hardware store or lumber yard soaking time app 10 minutes

Subj: Regarding: Thermostat Date: 97-01-04 22:09:54 From: Qshicks - do not run engine with out thermostat cooling system is a by pass system on all post 1969 motors and you run risk of damage from overheating and the temp gauge will hardly show any heat but block will over heat I have bin a universal dealer for 30 years and have seen several damaged blocks i don't know of any source for tstat except universal try your dealer if he cant help i stock them you can clean them and restore proper operation by socking in acid (muratic )get at hardware store or lumber yard soaking time app 10 minutes

Subj: Regarding: Thermostat/ Qshicks Date: 97-01-05 13:58:24 ED From: DJandon thanks Qshicks, Will try the acid test. The thermostat I have now looks good except that it won't even open at 200*. Please give me more d details on how I can get one from you in case the acid doesn't work on mine.

Subj: re thermostat Date: 97-0 1-07 18:40:58 ED From: MITCHELLRI If you choose to run the AT 4 without the thermostat, plug the hole in the inside of the thermostat housing so that cooling water will circulate throughout the engine block. T he engine will run cooler, and could result in sludge buildup on the valves, depending on how warm the water is where you sail. In salt water cooled engines, cooler is better, as the cooler temps retard the nasty effec ts of salt. If you convert to fresh water cooling with an exchanger, you can run the engine at 180, and it w ill like it and last longer. Your best bet is to get a heat exchanger for cooling your AT-4.I have heard the at AT thermostats can go for as much as $80.

Subj: Regarding:Thermostat Date: 97-01-08 12:15:26 ED From: T27boa t Hi, I think I heard that Universal now has available a 180 F thermostat which would be useful in FW C or fresh water boats only. I believe that most of the thermostats currently available from Boat US etc, are of the 140 F variety, which are good for salt water cooled engines. If I read DOn Moyer's most recent parts price list correctly he offers a used thermostat for $30. Don can be reached at 717/564-5748. He sails in the Annapolis area so would probably be familiar with the water you sail in. Good luck, Bill

Regarding:Thermos tat Date: 97-01-10 06:00:11 ED From: DJandon Thanks Qshicks, I tried the acid and it did the job. Now can I do the same for the engine? Thanks to all for your replies on thermostat. Dan...

Subj: Fresh Water Flushing Date: 97-01-10 18:01:27 ED From: VICKLC Can anyone provide information on a way to flu sh the raw water cooling system. Is there a home made rig for this purpose? (Please describe.)Are there anodes in the block?Where are they located in the block?

Re:ThermostatDate: 97-01-10 22:00:29 EDTFrom: Qshicks cleaning block yes you can but requires grate care and some replumbing if you are serious i will guide you through the steps

Regarding:Fresh Water FlushingDate: 97-01-10 22:06:09 EDTFrom: Qshick s to flush salt water cooled a/4 remove hose from sea cock place in bucket fill bucket with fresh wa ter and run moter . note no zink on salt water cooled a/4 happy tinkering

Regarding:Fresh Water Flushing Date: 97-01-11 15:44:59 EDTFrom: BrianRJohn I have a Prestone Antifreese flush addaptor on my inlet h ose. It is a "T" that connects the two ends of a cut inlet hose with barbed fittings and hose clamps. The oth er side takes a regular garden hose connection. When there is not a garden hose connection, a solid cap screw s on and just lets everything work as normal. To flush, close the thru hull, connect a hose and run the engin e with fresh water from the hose. I use this system to get a biodegradable antifreese into the block for wint er (I commect a stub piece of garden hose and put the hose into a gallen jug of the stuff and it gets sucked into the warm engine,,,, you must warm up the engine first so the thermastat is open so it gets into the blo ck. )They can't cost more than a few dollars at an autoparts store and can be real handy..

Regarding:Fresh Water FlushingDate: 97-01-12 13:11:59 EDTFrom: Qshicks never fead water to moter under presher y ou risk serious damage if engin stalles or dosent start or back fires allwayes feed from a bucket /open at t he top NEVER/NEVER NEVER BAD BAD BAD IDEA presher feed may damage water pump

Regarding:Fresh Water Flushin gDate: 97-01-13 12:32:51 EDTFrom: LRZeitlin This is a great idea. I use the Prestone T fittings on all lines that have to be prepared for winter, like the toilet input, fresh water system, etc. A stub hose l ed into a 5 gal. bucket of antifreeze solution works fine. To flush the engine, I lead the stub hose into th e bucket, start the engine, then add a trickle of water from a garden hose as needed to keep the bucket almos t full. I run it until the engine warms up, stop the engine, add antifreeze to the bucket, and let it run unt il nearly empty.

Regarding:fresh water flushingDate: 97-01-26 22:35:54 EDTFrom: MCPapa58 La st time I hauled out I just put a tee above my raw water inlet with a 1/2" ball valve. When I come in I just hook the end of a hose to it and turn on the fresh water while the engine is running. It only takes a minut e to flush out the salt water. My raw water strainer opens at the top so sometimes I'll just dump a gall on of freshwater in after I close the raw water intake.

Regarding:fresh water flushingDate: 97-01-26 2 3:14:53 EDTFrom: Qshicks never fead water to engin from a pressher source feed from top of sea st rainer or from a open bucket sierious risk of flooding motor damanging pump waterin oil bent rods or broken crankare all posabile with pressher feed very bad idea

engine running hotDate: 97-03-20 13:12:19 ED TFrom: GGDFGF after looking at previous post. I was thinking of getting a five gallon bucket fil l it with acid and flushing the internal cooling to remove the salt deposits that are clogging. has anyone done this ?

Regarding:engine running hotDate: 97-03-20 15:15:55 EDTFrom: Qshicks yyes do it all the time but be verry carful acid will react with mineral and fome and boil and fume up the in side of boat we youse a covered bucket witn hose barbs instaled [bilg pump overbord fiting work well and are acid proof sugest you by cheap oil change pump the kind that fits in a drill moter and throw it away when done since the seals fail after the acid treatment note 1 gall is plenty

Regarding:engine running hotDate: 97-03-20 21:48:50 EDTFrom: LRZeitlin Use an oxalic acid solution. You can buy oxalic acid at any paint store. Don't use muratic acid (hydrochloric) or battery acid (sulphuric).

Regarding:engine running hotDate: 97-0 3-21 09:53:54 EDTFrom: Qshicks why not youse hydrochloric/murratic witch is watered down hydroch loric after 40 years of cleaning heat exchanger and blocks with acid witch is a verry nasty job is thair some thing i am missing job should be done with grate care and all safety meshers in place we do app 40 job s a year smalest heater core to heat exchanger witch service 2000 ci moters in tug boats and hold 15gall o f acid and if you ever had the tankless hot water in your ferance cleaned i will bet it was with an acid wash and flush

Regarding:engine running hotDate: 97-03-21 13:03:20 EDTFrom: LRZeitlin Qshicks - you are a professional with 40 years of experience using the industrial strength stuff. Also, time savings mean m oney for you. Oxalic acid works just fine on scale and rust even though it takes a little longer. It is easy to get in paint stores and causes far less damage to skin and clothing when droplets of it are splashed aroun d. Have mercy on the occasional user. - Larry

Regarding:engine running hotDate: 97-03-21 19:02:12 EDTFrom : Qshicks point well taken labor cost is a large part of cleaning plus desposing of wast materal we add a cemical to nutrilize acid and just flush we yous to use baking soda but now with EPA require aprov ed materal cost 33% of acid so it is get in and get out or job gets to expencive and customer is un happy most of our customer have bin with us along time so they must be happy

Regarding:Fresh Water Cooling Date : 97-04-27 20:54:30 EDTFrom: Scubacon1 Just finished with the installation of a fresh water coolin g system, I installed a new stainless steel water jacket (Moyer Marine) and the Heat Exchanger from Moyer Mar ine, the new water pump andhookup parts came from Indigo Electronics...Between the guidance of Don Moyer and Tom Stevens (Indigo) the system is in and running I have never seen the engine run so nicely..I had looked i n every nook and cranny and asked a lot of advise from Qschicks and Moyer and Stevensbefore taking the task in hand ..I needed to redrill, tap and use larger bolts on the side plate..due toage and corrosion of that a rea from nearly 22 years of salt water intrusion into the engine.I was a bit leary of doing the job...I have to thank all those of you who responded to my Questions in the past.This gave me the courage to thrust forwar d and did a big favor to my faithful Atomic 4 engine..BTW you gotta get your hands on the coffee mug Don and Brenda Moyer sells it has a drawing ofthe Atomic 4 on one side and all the tune up specs on the other...My hat's off to both Tom Stevens (Indigo) and The Moyers for their help and guidance....sorry for being so winde d..Bob Studen S/V Silent Passage 1975 Pearson 10M sailing out of Oyster Bay LI Sound N.Y.

Regarding:Fresh Water Cooling kits Date: 97-04-28 20:49:22 EDTFrom: Qshicks kits run between 600.00 and 1000.00 depending on stile ie ware it instaled on engin or off engin driven elect and how compleat the kit all kits have a pump and a heat exchanger but some kits that is all you get you will have to provide all mounts and hose and fittings and sea strainer and thair is a big diferance in quality of parts it comes down to pay me now or later i have a custmore with an elect driven sea water pump on a a4 1n a launch just no room fore e ngin driven. heat exchanger in bow lots of hose but system is 6 years old pump is inspectsd every season but no troubel If thair is a will thair is a way also nead deep pocket over 8 man hours in instalationplus pa rts boat is 16 long and 0nly 4 ft wide and 30 hp 1800 rpm gives just a hair under 8 knots lots of fun owner lets me borow it now and then.

Water Pump ImpellerDate: 97-06-11 08:27:37 EDTFrom: CptnRn I just found that West Marine has a replacement impeller that fits the A4 Oberdorfer water pump for $15.00. I ordered one and it looks like a perfect match.Its advertised as more resilient, self lu bricating, more resistant to sand and debris abrasion and guaranteed to withstand running dry for 15 minutes. Not that I recommend doing that, but if its more resistent to breaking into pieces it can save you a lot of trouble looking for the missing parts that got sucked up into the engine.It is a long life Niprene impelle r replacement made by Globe, #815, for $15.00, West Marine, Page728, #241044. Oberdorfer Water pump impell er: The impeller is 2" diameter, 7/8" wide, w/ a 1/2" dia. single flat drive.ArchTx

Regarding:Water pump impellersDate: 97-06-17 08:37:05 EDTFrom: Yeocomico I think West Marine now carries them, they ar e blue I think, check in Cataolg, or post a note in the folder here. Supposedly will run 15 minutes dry. S ubj: Regarding:Water pump impellersDate: 97-06-17 18:59:17 EDTFrom: Qshicks to my knowalage thair has bin [2] jabsco [1] sherwood [1]obendorfer pump instaled on the a/4 over the years and thay all youse diffe rant impellers with one do you want an impeller fore

Regarding:Water pump impellersDate: 97-06-17 20:57:5 7 EDTFrom: T27boat Depco Pump Co. in Clearwater Fl has been easy to do business with. They are at 1-800-445-1656 and will ship with a credit card. Don Moyer also stocks water pump parts at 717-564-5748. Han son Marine in Marblehead MA at 800-343-0480(Westerbeke/Universal Distributor ) also has all the new parts ava ilable.Bill

Regarding:Water pump impellersDate: 97-06-18 08:41:38 EDTFrom: Bristol32 Another qu estion, a friend has a Tartan 27 1963-64 vintage A-4 in it. He recently took the water pump apart to see if the impeller was still there, and found brass gears. Did they install a gear pump on these things? I can't imagine why. He took it apart because his water flow out of the exaust was small, and had some steam too. A lthough he can keep his hand on the head after 30 minutes of motoring, so we don't think it is overheating. Any reason to be concerned?

Regarding:Water pump impellersDate: 97-06-18 11:55:34 EDTFrom: Bristol32 The A-4 on my Bristol has a Oberdorfer made in Syracuse if I can read upside down.

Regarding:Water pump impellersDate: 97-06-18 18:36:24 EDTFrom: Qshicks gear pumps was standerd on verry early a/4 and as it still workes he can still youse it the lack of flow could be pump ware or just the block plugi ng up and in nead of a clean out or the exhaust pipeing pluging up to test pump remove hose and start moter-D and watch pump out put about 3/4 gall a minute at idel speedend

Subject: Atomic 4 Took my newly bought 1966 Coulmbia 29 out for the first time yesterday. There is no thermostat on the original Atomic 4 engine. A lever opens and closes the water cooling bypass system. I found myself watching the temperature cold...jump down to open the valve...jump back down to close it...up and down. A real pain in the ass. I felt like Mr. Arenaught on the African Queen. I'm sure there is an optimum setting for this bypass valve but I wonder if I couldn't just have something put on the engine to regulate the cooling a themostat.

I bet if you look at an atomic 4 service manual you will find that there originally was a thermostat on your engine. it is typical for atomic 4 owners to install a bypass valve to control overheating as an older engine begins to run warm. the bypass allows water to run through the exhaust system to keep it cool, while simultaneously forcing water throught the block.

check the gooseneck on the engine, if it has a plug sealing off an outlet hole, you originally had a thermostat.

((Took my newly bought 1966 Coulmbia 29 out for the first time yesterday. There is no thermostat on the original Atomic 4 engine.))

Yes there was, read on.

lever opens and closes the water cooling bypass system. I found myself watching the temperature cold...jump down to open the valve...jump back down to close it...up and down. A real pain in the ass. I felt like Mr. Arenaught on the African Queen.

Move the valve small amounts, you were overcontrolling, see below.

I'm sure there is an optimum setting for this bypass valve but I wonder if I couldn't just have something put on the engine to regulate the cooling a themostat.

Yup, if you want to $pend for it, but it's not really necessary. At the top front of the block, there should be a domed housing, that's where the thermostat should go (the hose from the bypass valve should go into it). I don't have a thermosat in my engine because the housing has a bypass passage that is corroded in mine, and a new one is about $65 and about $30 for the thermostat. It's expensive because the thermostat 'steers' the water by taking it from the bypass (which should always be all the way open if a thermostat is installed), or from the block. It does this because the water needs to flow through the manifold and out through the wet exhaust all of the time to prevent burning the manifold, or exhaust system. There are other ways to accomplish this, but that's the way the Universal designed it for the A 4.

In any case the extra 'stuff' in the thermostat and housing are what makes it expensive and why most folks leave them out.

I just leave the valve open all the way and the engine runs at about 90 - 120 degrees all of the time. You do not want a raw salt water cooled engine to run much above 120 because some salts will start precipitating out of the water at about 135 (really, they do. Calcium and magnesuim salts, I believe). These salts can clog cooling passages in the engine. Filling the engine with plain white vinegar and leaving it there for 24 hrs will remove most of these deposits.

If you want to adjust the valve for a particular operating temp, run the boat at cruise speed for about 15 min to stabalize the temp with the valve open. Start closing it about 10 degrees of rotation about every 5 min until you get to the desired operating temp, then open it back about 5 - 10 degrees. Then leave it alone, the temp will go up 10 - 20 degrees when you pour it on to get under a bridge in a foul current, and it will cool off by the same when you are motoring downwind, etc.

Unless you install a freshwater cooling system with a heat exchanger, run the engine cold. Put about a pint of Marvel Mystery oil in the crankcase at every 25 hr oil change (important since there is no oil filter on an A4) to keep the rings from gumming up due to the low operating temp. MM oil is amazing stuff, it's been around forever and it will keep the insides of your engine free of crud.



Subject: Cleaning Block? Date: Wed, Sep 10, 1997 12:58 AM From: JDJahnke

I fear that I may have the same problem as the owner of the MD-7A. I have an MD-2 that uses raw water for cooling, and now frequently overheats. I suspect its getting scaled up inside. I there any way to clean the water passages in the block with out taking the engine out and acid bathing the whole thing?

Subject: Re: Cleaning Block? Date: Wed, Sep 10, 1997 2:41 PM From: LRZeitlin

There is a simple way to clean all raw water cooled engine blocks. It involves circulating an oxalic acid solution through the block until the scale is dissolved, then neutralizing with baking soda.

1. Close the raw water intake valve.

2. Remove the water pump impeller and put back the cover.

3. Disconnect the water intake hose from the intake valve.

4. Remove the themostat. Replace the cover.

5. Disconnect the water hose which injects water into the exhaust.

6. Fill a five gallon bucket with warm water and dissolve two pounds of powdered oxalic acid (obtainable from paint stores) in it.

7. Using a Water Puppy pump or equivalent, circulate the oxalic acid solution through the water intake hose, through the block, out the exhaust outlet hose, and back into the bucket. Do this for at least two hours or until no more crud comes out of the block.

8. Empty the bucket and discard used solution safely.

9. Refill the bucket with two lbs. baking soda dissolved in 5 gallons of water. Circulate for at least 15 minutes.

10. Reconnect engine hoses, install thermostat and water impeller. Your block has been cleaned. Good luck, Larry

Instructions on an acid flush out for the cooling system.

Qshicks: Jul 4, 1998

re your request as to how the cooling flow on the a-4 post 1969 works this is how it works the salt water pump takes a suction on the sea strainer and delivers the water under presher to the [T] fitting in the side of the block it all so delivers water to the fitting on the side of the thermastat housing ware if the moter is cold [less than 142 degres the water flowes over the top of the tstat and out the fitting at the top of the houseing and to the exhaust manafold and over board when the motor warms up the t stat will start to open the port in the cilinder head and allow water from the block and head to flow to the exhaust manafold and over board at the same as the t stat opens it closes the buy pass port off causing the water from the pump to flow into the block and the head if you look at the t stat housing in side the top of the stat seals off the port from the buy pass line note thair must be a good flat seating serfice in side the housing or the system wont work correctily it is the closeing of the buy pass line that forces the water through the moter note i will not sell a new t stat un less the coustomer brings in the housing for me to see at least half the time the houseing is at falt and not the stat since you have the motor apart have the machine shop bake out the block to remove thr rust and scail that you cant reach to remove .have them do it wile thay do the valve job hope this helps qshicks

Subject: Re: Cleaning Block? Date: Thu, Sep 11, 1997 3:31 AM From: RHolman240

Is there any chance of damage to gaskets or seals from the oxalic acid? It sounds like a great idea.

Subject: Re: Cleaning Block? Date: Fri, Sep 12, 1997 7:05 PM From: LRZeitlin

Oxalic acid is pretty mild stuff compared to the hydrochloric acid that professional rebuilders use. I've never had any problem with the gaskets but the only ones at risk are the impeller and thermostat gaskets, both cheap to replace. In fact, any time you open the water pump or thermostat housing it is a good practice to replace the gaskets anyway. The head gasket is made of much stronger stuff and two hours in oxalic acid will not damage it appreciably. Don't forget to neutralize the acid before finishing the job. - Larry

Tip on recirculating the water: One of those cheap pumps that hook up to a drill will do the job. Its the perfect tool note you dont have to run the pump all the time once every 10 minuts will work just as well to clean and nutrialize the acid desolive a pound of baking soda in a bucket of water and run that through the moter then flush with fresh water dont forget to retork the t stat housing bolts thay are head bolts [35foot lbs ]



The Universal Motor Company started business as a marine engine manufacturer and the A-4 was designed from the ground up as a marine engine. It even utilized special corrosion resistant metal alloy's. Of the 40,000 A-4's originally installed between 1947 and 1985, in boats from 25' to 41', around 20,000 of these reliable little engines are still in use. At thier peak Universal had 85% of the sailboat market. For more interesting facts on the history and design of the engine, visit the

Atomic Four Engine Service

web site, by Robert Hess.

CANADA - Robert Hess. Sells rebuilt engines, parts and accessories Atomic Four Engine Service, 5017 Mariner Place, Delta, BC, V4K 4J4, Canada Telephone: 604 (868-6646) email:


RE: Engine Design: You raise an interesting point about the number of cylinders that a boat engine should have. There is sort of a rule of thumb among boat designers that a displacement boat should have about one horsepower per 500 lbs. of displacement to move at hull speed. This accounts for loses in the drive line and propellor inefficiencies. My 16,000 motorsailer would thus require about 32 hp. A 30 hp A4 would suffice for a 15,000 lb hull.

Automobile engineers tell me that a modern gasoline engine can be expected can be expected to deliver a maximum output of between 50 to 100 hp per liter of cylinder capacity; and also, that the optimum size for each cylinder is about 500cc. The more cylinders, the smoother the power flow and the less the vibration. For continuous use and high reliability, they prefer to cut the expected maximum output in half. Thus each cylinder in a continuously rated, conservatively designed boat engine should put out from 10 to 20 hp.

Using this logic, it seems reasonable to specify two to four cylinder engines for most sailboats. I guess manufacturers prefer lighter, simpler designs and assume that we will tolerate engine roughness in boats that we would reject in autos. I, for one would like to see a small, light, inline 6 cylinder engine in the 50 hp range to replace my aging Perkins 4-107. After all Ferarri and Jaguar had 12 cylinder engines and Cadillac a 16 cyl. engine.

I guess we will have to wait untel fuel cells come along for the ultimate is vibration free power. - Larry Z



(See Cooling System also)

CANADA - Robert Hess. Sells rebuilt engines, parts and accessories Atomic Four Engine Service, 5017 Mariner Place, Delta, BC, V4K 4J4, Canada Telephone: 604 (868-6646) email:

This web site has an excellent history of the Universal Motor Company and the design of the Atomic Four engine. I thouroughly enjoyed reading the information provided there. Robert Hess also provided some information that seems so important to Atomic Four owner's that I'm reproducing it here. His business is rebuilding these engines so I think it is prudent to listen closely to what he has to say. It has inspired me to go out and buy a timing light.

etting the ignition timing by adjusting the distributor while the boat is under full power ("power-timing") can sometimes result in excessive ignition advance, which can contribute to head gasket failure (or worse). Pre-ignition and detonation (knocking) caused by excessive ignition advance or high compression can cause head gasket failure, cylinder head combustion chamber damage, piston crown collapse, piston compression ring and ring land breakage, valve face failure, and connecting rod bearing damage. Poor grades of gasoline (usually found in third-world countries) with octane ratings below 89 make lowering the compression ratio through the use of two gaskets more important in order to reduce head gasket failure or other damage. Although leaded fuel was originally designed to reduce engine valve seat failure as well as raise gasoline octane rating, especially in engines such as the Atomic Four which do not use hardened (Stellite) valve seat inserts, the use of unleaded gasoline in the Atomic Four does not normally cause any damage to valve seats as long as the valve clearance is properly adjusted and stock valve springs are fitted. For that reason it is considered more beneficial to add octane booster when the fuel octane rating is below 92 than it is to add a lead additive to unleaded fuel.))

I Have a blown head gasket in an atomic 4. Any ideas? ) Thanks, ) Mike ) Charity in New Orleans

Mike, I read what Alan wrote and agree with his recommendations. I have never tried a NAPA dealer before (mainly because i too get the blank stare - I never tell them it is for an atomic 4 - i just tell them the part number i want or equal). I have changed the head gasket twice on mine. Gasket kit is about 90 bucks, got one from a local dealer (private shipyard), the other i ordered from Old Lyme Marine in Old Lyme CT. They will take all the colors (AMEX, MC, VISA) they will also ship overnite or UPS (cod with check okay).

I don't want to insult your intelligence, but be careful and fix the problem, not the sympton. Low compression may also be a sign of ring/cylinder problems, or valve adjustment problems. In order the tell the difference, use a threaded compression tester (from auto store - dont use the ones you have to hold on, you cannot get an accurate reading given the normal location of the A4) and complete the following.

1. Go to Capn Ron's homepage http://members.-/CptinRn/ and download the A4 manual.

2. Shut off the gas supply to the engine.

3. Label all the plug wires with the cylinder number.

4. Use a paint brush and remove any dirt from around the spark plug, then remove the spark wire/plug from the #4 cylinder.

5. Screw in the compression tester, turn the engine over, and record the compression. (should be 90-125 psi).

6. Reinstall spark plug and wire.

7. Repeat steps 4 thru 6 for the remaining cylinders.

IF it is a head gasket problem there will be abnormal low readings between two adjacent cylinders (the area between adjacent cylinders is about 1/8th inch much smaller than the distance between the cylinder and the edge of the head - you do not normally see the head gasket blow out to the side).

IF it is a ring or valve problem, the pressure should be low across all the cylinders. Which does not require replacing the head gasket.

IF Replacing the head gasket, proceed as follows:

1. Get the new gasket, it will be either green or a silvery/graphite type gasket, you will only need one.

2. Go to auto store, buy a couple cans of spray gasket remover and a gasket scraper.

3. Secure the water to the engine, and drain it down, close and rope shut the seacock serving the engine (if no seacock, buy a PVC plug and install).

4. You may have to remove the alternator and bracket, plus th ewater lines to and from the head.

5. Remove the head, if the stud starts turning, that is okay, let the stud come out.

6. Once all the studs are out, the head may not come off. There is no tabs to use for prying the head off. I used a narrow paint scraper (yes i know it may scratch the head, but it is better than using a screw driver). The paint scraper may have to be worked all around the head. Do not use it on the exhaust manifold side, the valves are there. You may need a rubber mallet to help persuade it to come off. Be gentle and work it.

7. Once the head is off, remove the studs, if less than three threads left, either try alan's fix or just get new studs (heat treated) and save the helicoil fix for a later day.

8. Scrap the old gasket off the block and the head.

9. (optional step - take head to auto shop to check for flatness. If not flat, they may "shave" it for a nominal fee).

10. Put new gasket on, if your lucky the torque spec and pattern will be included with the gasket. I think 25 is right, will look up tonight, make sure the alternator bracket is on if removed.

11. Reconnect your water lines, open seacock and fuel line - start engine.

12. Allow engine to warm up - 5 to 10 minutes then shut down, re-torque to proper torque in proper manner.

13. PEP Boys (manny, moe and jack) have a spray paint real similar to the original A4 color, hit the head to make it look nice.

14. Go sailing and congratulate yourself on your engineering prowess!!! Regards, John Blais ps - 1st time i did it in the boat, but removed the forward engine bulkhead and stairs - gave me plenty of room on the P30, second time took the engine out.



Regarding:Water-lift mufflerDate: 97-04-28 20:54:01 EDTFrom: TALISMANIA Thanks for advice from QShicks and BrianRJohn. I expect I'll find that muffler itself is fine but just need to clear all obstructions and perhaps replace some hose connections. Of course, you have to be a conto rtionist to get access! Are either of you on/near the Chesapeake? If so, I thought you might know name of good Atomic 4 mechanic. Don Moyer's newsletter has been a great source of advice over the years, but it's n ice to have a reliable engine shop close by.

Matt wrote: ))After reading some old posts on raw water cooling, I became concerned. ))The saltwater cooled A-4 in my Pearson Triton blows steam out of the exhaust ))when ever the engine is run (although this has been less than 30 minutes )since ))I bought the boat a week ago.) The temp gauge has never shown much over ))140-145 degrees. ))What might the exhaust steam indicate? Do I have an overheating problem? Is ))this just condensation due to the cool outside air temp?Thanks. )) ))Matt Peterson- "Aweigh," Triton #379 ))Alameda, CA )

Ron Wrote: )There are different thermostats recommended for raw and fresh water cooling.

)Temperature: 150-165 degrees w/raw water cooling.

) 180-190 degrees w/ fresh water cooling.

)However, that said, I have raw water cooling, and even with a new thermostat )installed the engine temperature seldom gets up to 150 degrees in the winter )when the bay water is around 50-60 degrees. Unless of course the impeller )looses a blade or two.

The following provided by Rich H. was an excellent response to the original question. I've been puzzling over ways to improve my exhaust system as what Pearson installed seems really cobbed together (but it works). Rich could you explain a little more regarding what you called "the 'traditional' copper steam riser pipe" I don't believe I've seen one of those yet. The two A4's I'm most familiar with, my P-28 and a P-30, both used a 1 1/4" galv. iron pipe from the exhaust manifold up to the highest point in the engine compartment where there is a water injection fitting, which as I recall is nothing more than a brass hose coupling screwed into a reducer on top of a galv. iron Tee. Then a "rubber"(?) hose drops down to the water lift muffler and another '"rubber" hose runs up and then back down to the stern exhaust discharge fitting. I hope that makes sense.

)Rich H wrote: It is quite normal to see steam (visible water vapor) in the exhaust of an A4, especially if you have a wet muffler system. What you see under normal conditions is the phenomenom of 'dew point' which is the temperature at which vapor condenses visibly. In colder ambient conditions - the more visible the phenomenon. ))There are some quirks that will also lead the venerable A4 to produce more than the normal amount of visible water vapor: 1. blown head gasket, 2. blocked or partially blocked exhaust manifold. 3. rotted or missing "umbrella cap' in the steam riser pipe on older A4s. ))

1. Blown head gasket: Do compression test. Head gaskets usually blow-through between cylinders 3 & 4 for some reason. Engine will run almost perfectly since the compression ratio is quite low. If pressure variation between cylinders is somewhat equal, and you still think that there might be head leakage, you can get some indicating chemicals from an automotive speed shop and add these to the cooling water. This chemical will change color in the presence of carbon dioxide/carbon monoxide - indicating leakage through a partially blown head gasket. If your engine is seawater cooled, disconnect the exit cooling water line at the end of the exhaust header and run into a BIG bucket. Use a hose and connect from the bucket to the inlet of the cooling water pump. Circulate, according to the directions of the chemical and see if the color changes. Prevention: re-torque the head yearly. ))

))2. Blocked or partially blocked exhaust header. This part of the engine corrodes into large plates/sheets of rust which can migrate to the exit of the water jacket section of the exhaust manifold and block or restrict the outlet nozzle. The A4 has a normal cooling water circulation of 3 gallons per minute at about 1500-1800 rpm. Measure the flow and if less than 3 gpm, you will probably need to either replace (expensive) the exhaust manifold or wash the internals of the manifold with acid (cheap, somewhat dangerous). If blocked or partial blocked you will have to remove the exhaust manifold to clean or replace anyway, and then you can test for 'pin holes' between the gas side from the cooling portions (rare). ))

))3. If you have the 'traditional' copper steam riser pipe ( a 36" long 4 inch diameter pipe mounted vertically with one water connection at the top) there might be a problem with an internal 'welded' cap which prevents the final cooling water from getting back down the gas outlet.

))I have 'rewelded' this 'cap' several times. Symptoms are water in the gas side of the exhaust manifold after shut down. ))

))Hopefully all that you see is nothing more than normal condensating water vapor because of cooler temperatures and 'dew point'. If you suspect more, then the above can quickly steer you towards the

))problem.... The A4 is an elegantly simple and reliable engine. ))

))Sea water cooled engines are subject to salt build-up internally primarily; plus, the corrosion is somewhat accelerated. Max temperature for the thermostat is 170 degrees F for seawater cooled engines.

))Hope all this helps. ))regards ))Rich H. P30 #447

From: "Hess" Subject: Re: Water pump fittings - what type of metal

If there is any chance the material could be asbestos, don't try to remove it in the boat. You could end up with a boat full of asbestos fibres, which has been proven to cause lung cancer 20 to 30 years later. Don't try to vacuum the material off the pipe, because the asbestos fibres which cause lung cancer are so small they are invisible to the naked eye, and pass right through the filter in home and shop vacuums and end up nicely dispursed back into the air right where you are working. Wrap the assembly with a clear plastic sheet covering the insulation and duct tape it to the bare pipe at both ends, then remove the whole thing and dispose of it properly without disturbing the wrapping. If you must save the assembly, once you have removed it from the boat to a safe place to work as described above, wet the whole thing with water, remove the plastic, and wash the insulating material off with water into a drum which you can seal and dispose of properly. Never blow it with compressed air.

The standard Atomic Four exhaust flange is threaded for 1 1/4" NPT, and so most manufacturers used 1 1/4" pipe for the exhaust riser. The riser is insulated between the exhaust manifold and the water injection elbow, because that is the only part of the exhaust that is not water cooled, and it gets very hot. I make Atomic Four exhaust risers out of 316 stainless steel pipe fittings, but most manufacturers used black or galvanized iron pipe. Most manufacturers and marine repair shops now use a wrap of fibreglass tape held on with stainless steel wire or brass wire (some people use stainless steel hose clamps) to insulate the dry section of the exhaust riser. robert



Regarding: Atomic 4 Oil Change The following comments are compiled from numerous previous emails, with my own comments thrown in:

Dave wrote: ((Does anyone have any recommendations on how best to change oil on atomic 4 engine in a 1975 P30? It appears to have a drain into the bilge but not enough room to drain into anything there.))

There is an oil drain plug on the lower forward Stbd. side, which is also very difficult to get to on my P-28. The engine access on the P-30 seems to be a degree of difficulty worse all the way around. It is questionable on the P-28 if there is even room to remove that drain plug, but even if it could be removed there is no room for any kind of container to catch the oil. And if the motor is put in at an extreme angle of tilt the drain plug may not even be the low point of the pan (more about this later). I do like the idea of attaching a fitting and tube to this plug to pump the oil out, I think you could remove more heavy sediments from the plug at the bottom of the pan than you can when you pump the oil up thru a tube.

((The dip stick is in about the worst place I can imagine putting one. Is there any way to improve this arrangement.))

On "Mystic", engine access to the dip stick, distributor, water pump, etc. all require the removal of a perforated masonite panel, which is too troublesome for frequent checking of the oil. So I cut a 6" opening in the panel where I could pull the dipstick to check it more often. On the P-30 the engine may be mounted further forward so that you are into the side of the plywood cabinet below the sink, so this may not work.

[[I don't even know how much oil the engine should take.]] The Owner's manual says that it takes 4-5 quarts, however see the A4 Parts document regarding Oil Changes - http://members.-/CptinRn).

I posted this message some months back (March ?, 98):


I only recently learned that the amount of oil that an Atomic Four engine can hold varies with the angle of tilt which it is installed at. Most Pearson hull sections that I have seen indicate that the engines are installed at around 14-15 degrees, which is the maximum recommended by Universal. My Owner's Manual says the engine should hold 4-5 quarts of oil, this always puzzled me because I can typically only remove/add 2.75 quarts. I had thought that the angle of tilt kept me from pumping the other 2.25 quarts out of the engine. NOT TRUE! At the extreme angle of tilt, the total amount of oil that your crankcase will hold is only 2.75 quarts (See the oil levels table at the Alberg 30 A4 site - With this small quantity of oil available to lubricate your engine, it is extremely important to check and change the oil often, OR if you can afford it, install the Indigo oil filter kit."

In Don Moyer's A4 April 98 newsletter he responded to this:

"It takes approximately 4.5 Qts of oil to reach the full mark in a "dry" engine, just after an overhaul with the engine setting level.....After turning the engine over to fill all the internal passages within the oil system another Qt is required to return the level to the full mark (5.5 Qts).....If the engine is tilted so as to approximate the highest angle that one would expect in service (?*), the engine holds approximately one quart less (4.5 Qts).....With the Engine tilted as above it is only possible to pump out slightly over 3.5 Qts (?**). With a bit more or less tilt, it may be possible to remove more or less during an actual oil change"

?* He doesn't define what this angle is, the Owners manual says Maximum operationg angle---approximately 12-15 degrees maximum.

?** Since I can pump out only 2.75 quarts this tells me that my engine is mounted at a higher angle of tilt than what he was using. If you use a protractor on the Pearson diagrams most of the engines are at or more than 15 degrees of tilt. I have not measured the actual installation on my boat yet.

Don M. recommends using the dipstick full mark regardless of the angle of tilt, rather than trying to add more oil to make up for it. He emphasises the importance of changing your oil every 50 hours or once a season, whichever comes first (use 30 weight). My point is that if you have an installation similar to mine,where you can only pump out 2.75 Qts, that leaves 1.75 Qts. of dirty oil in the crankcase, so it may be a very good idea to change your oil more often or install the Indigo filter kit. Another option would be to change your oil, run the engine for a few minutes to dilute the dirty oil, then change it again so that you effectively remove more of the dirty oil.

Several people recommended the vacume can oil changer. I bought one, a Topside SumPump, several years ago and was disatisfied with it, because I couldn't remove more than 2.75 Qts of oil from my A4 engine. Now that I understand why, I realize that perhaps the pump wasn't the problem. It was much easier to use than a hand pump. But I still don't like having to crawl down into the lazarette to change the oil, so I did this:

LET THE OIL PUMP REMOVE IT: I once saw an advertisment for an expensive valve device that attaches to the oil pressure gauge connection that allows you to drain oil off while the engine is running. It had an automatic pressure sensor that closed it when the pressure dropped, so you don't damage the engine. This part of the engine is easy for me to get at, so I figured I could do the same thing. I added a brass tee fitting to the oil pressure gauge pipe (on the A4 it is to port forward of the carberator) so I could add a valve & short plastic hose to it. After the engine has warmed up, and is running at an idle, I open this valve a little bit and let the engine oil pump discharge the oil into a plastic container. All I have to do is sit there and watch the oil pressure guage and the discharge, I have found that the pressure never drops until the discharges starts to pump small air bubbles with the oil and then it drops slowly. At this point you still have a quart or more of oil in the crankcase, depending on angle of tilt. I then close the valve, add a quart of oil, let it run awhile to dilute the old oil and then continue pumping. If its been awhile you might want to do this several times to flush out as much of the old oil as possible. When it starts bubbling again, close the valve and top up the engine with new oil.

Some people think this is a risky method, but I believe as long as the oil pressure is kept up, there is no risk. You definitly don't go walking the docks BS'ing while the oil is pumping out. But you can sit there comfortably and drink a beer, watching the engine do the work. I've been told that this method is used on many commercial ships with much larger engines. Use this idea at your own risk.

Fred Dammann wrote:

((John: Have been wondering if the port side pipe plug you mention could be used for a dip stick hole as well as a drain hose hole.... I have a terrible time trying to check oil level - can get the dip stick out but can't find the hole when putting it in. ))

Fred, It should be relatively easy to do this. You will have to calibrate your new dipstick so that it matches the old one for fill levels.

[[I think the atomic 4 i have is great....except i really cant understand why they designed this engine without an oil drain in the bottom. I have a V drive on my boat, so the engine sits backwards. this would make it real easy to get to a plug in the rear of the engine.....if there was one.))

There is one on the bottom port side (on your boat) of the oil pan. You can pump out of the oil dipstick or drill, tap and install a pump out line thru the transmission access cover plate.

(( The only thing you need to be VERRRYYY careful about is the old dipstick location was calibrated for the proper levels and installation (i hope!! - I don't even want to think about the answer to this question, but is the full mark on an A4 on a P30, in the same place as a P10M and a P35?, i think the engines are mounted at different angles - or does it not matter?).))

Don Moyer says this was taken into consideration, in fact the older models of A4's had a dipstick which had different markings for different angles of mounting, but Universal decided that wasn't necessary and discontinued it on the newer models.

(( For those of you who have Atomic 4's and who may also subscribe to Don Moyer's "Atomic 4caster" newsletter, Don sent a brief letter accompanying the latest newsletter to say that April 1999 will be the last publication of this newsletter. I suspect that Don will still be around at Moyer Marine to aid and assist those of us who maintain our A4's, but it is a sad passing to see his newsletter disappear. I'm just passing this along for general info. If you need more information, pls contact Don directly at 717-564-5748, fax 717-564-5760. Send mail to:

Moyer Marine Inc. 3000 Derry Street Harrisburg, PA 17111))

Only the newsletter is retiring. Don Moyer is remaining in business and concentrating on repairing engines. He has compiled a collection of newsletters that will be published as a "Service and Overhual Manual" and will be available for purchase. Fair Winds, Ron wrote: ((The Atomic 4 on my 1978 Catalina 27 seems to lack both an oil filter and an oil drain plug. The engine nameplate says model 5101. Can you help? ))

I'm not a mechanic, just a poor Atomic 4 owner, trying to keep it alive as long as possible. But I think I can help.

The A4 wasn't made with an oil filter, so its very important that you change the oil often, every 40-50 hours of use. An after market oil filter kit is available from Indigo (see attached zip file for the parts list).

Use 4-5 quarts of SAE30W heavy duty. The amount will vary depending on how steep a tilt your engine was installed with. Do not use any of the newer multi viscosity oils 10W- 30W etc. Don Moyers recommends MARVEL MYSTERY OIL about 10 oz (correction 4-8oz) to 10 gallons of fuel and about one quart in the crankcase to replace one quart of regular lubricating oil, to keep compression rings from sticking. It also helps lubricate the valve stems.

The attached A4 owners manual shows on page 5 an oil drain plug on the bottom, starboard side, forward corner of the engine. If this is not accessible (mine isn't) or your motor is installed an an extreme tilt, it may not drain all of the old oil from this location.

Page 16 of the manual recommends using a hand sump pump for the oil removal (with a small tube down the dip stick hole). I've never been satisfied with these hand pumps or the "Topside Pump" which sucks it into a metal tank, perhaps because the dip stick side of the engine is still hard for me to get to.

I once saw an advertisment for a valve device that attaches to the oil pressure gauge connection (port forward of the carberator) that allows you to drain oil off while the engine is running, it had an automatic pressure sensor that closed it when the pressure dropped, so you don't damage the engine. This part of the engine is easy for me to get at, so I figured I could do the same thing. I installed a brass tee fitting to this connection so I could add a valve & short plastic hose to it. After the engine has warmed up, and is running at an idle, I open this valve a little bit and let the engine oil pump discharge the oil into a plastic container. I sit there and watch the oil pressure guage and the discharge, I have found that the pressure never drops until the discharges starts to pump air bubbles with the oil and then it drops slowly. At this point you still have a quart or more of oil in the crankcase, depending on angle of tilt. At this point I close the valve, add a quart of oil, let it run awhile and then continue pumping. If its been awhile you might want to do this several times to flush out as much of the old oil as possible. When it starts bubbling again, close the valve and top up the engine with new oil.

Some people think this is a risky method, but I believe as long as the oil pressure is kept up, there is no risk. You definitly don't go walking the docks BS'ing while the oil is pumping out. But you can sit there comfortably and drink a beer, watching the engine do the work. Use this idea at your own risk. Fair Winds, CptnRn



Deragon Painting Atomic-4

The greatest stuff ever for treating crusty flaky metal is a blue liquid that is the consistency of water that cold galvanizes metal overnight- since discovering it while I owned a 1914 built boat with lots of crusty stuff and need to seal iron to stop "bleeders" from wrecking my hard earned paint jobs and varnish, I use it on everything. It's called "Ospho", NOT a marine product and very reasonable. Comes in a 32 oz plastic bottle.

All that is required is to get the loose stuff off, then wait overnight after soaking a rag and wiping the metal- I found it worked great on the old Graymarine 4-banger in my boat, takes prime and paint better, and the engine paint sticks and doesn't rust through. The metal turns gray from brown crust color, like it was galvanized. Found at any good hardware store.

DON MOYER sells a bronze spray paint that matches the original A4 color.



Subject: Spare parts in Bahamas Date: 28 Aug 1997 21:41:20 EDT From: Yeocomico

Another question. What would you take with you on a 5 month cruise in Bahamas in the way of spare parts? Here is my list, any other item come to mind?
Spare alternator
spare water pump and gaskets
several impellers (3)
spare fuel pump (electric to replace the manual one)
fuel filter cartridges (3)(spin on kind)
fuel line
set of spark plugs
water hoses
alternator belts(2?)
rotor cap (I have almost new points, plug
wires, cap and condenser and coil from pre electric ignition)
marine grade wire and crimps,etc
packing flax
Spare propeller?
misc hose clamps.
exhaust hose?
Tools (hand crank, sparkplug wrench, gap gauge, general wrenches, screwdrives, teflon
tape, flax puller)

Is the funnel/filter worth it for prefiltering gas as you fill the tank?

spark plugs
distributor cap
spark plug wires
spare coil
fuel filter
spare filter element
moter oil
timeing lite
water pump greas
carb gaskets and a needle and seat size 25



Qshicks: Engine Replacement: universal mini 3 will replace your old a 4 it is app 1 inch taller and 1inch longer and fitts the same 11/1/2 centers that the a/4 did note you will need new controle cabels and a new exhaust system and maybe a new fule tank depending what the curent one is made of allso a new fuel strainer and a sea straner I am a dealer and replace a fair # each year I would figuer 1500.00 above the price of engin are you going to do the worke your self or have adealer do it you can e mail me. about fuel #2 diesal has 33% more BTU than gas for the same weight of fuel. hence more range Onthe question of weight 3gm is lighter.



RE: cruising RPM's GSTDGriff@- wrote:

) I'm guessing that all these boats are underpowered, a decent general rule of ) thumb is one hp per 500 lbs. So a 10k boat should have 20 hp. )

According to Hewitt Schlereth, in his book, How To Buy a Sailboat; most sailboats are actually overpowered. This is because they only require power to push them at hull speed, not planing speed. The formula he suggests is displacement in tons times 3.

That would make a 9000 lb boat; 4.5 tons, be adequately powered with a 13.5 hp engine. He does make the point that an overpowered engine doesn't have to work as hard and therefore, not cause as much vibration. Dave Weilacher Jax Beach, Fl.

Subject: Re: Cruising RPM's Date: Thu, Oct 1, 1998 4:52 AM From: RHmpL33

The best way I know is to do actual testing as follows: With a clean hull, a free turning stuffing box, and well running engine, etc.- record various boat speeds versus the corresponding rpm, including the maximums that your boat can perform. Use or make chart paper with one axis the knots and the other axis the rpm. You will for the lower values develope a straight line plot. With increasing values the plot will extend straight until you start to see the line you plotted start to curve. Just before where the plot starts to curve is the maximum 'cruising rpm'. This 'knuckle' in the plot will also very closely correspond to your boat's actual hull speed. Its a simple method, isn't theoretical, and is independent of tachometer and knotmeter errors (just as long as you dont change the instruments). Its very interesting that most large stinkpot drivers I know have such a curve/plot to see where they are efficient in rpms vs. speed. For instance if they exceed this knuckle in the curve, they usually make a call to their bank for another loan for fuel. In contrast, most rag boaters almost never have this kind of data. Hope this helps. If you try this let us know how it works out. Best regards. :-) Rich

PROP: IndigoAT4 : Having just purchased a '76 Tartan 34 with Atomic 4, the very first thing I did was replace the prop. On many of the older boats, a 12 x 9 pitch prop seemed to be a favorite. They would get the boats up to top hull speed and they were velvety smooth because they were only turning about 1400 RPM. Unfortunately, you had no reserve power for those days when you were trying to drive against a 25 kt headwind plus you were essentially " lugging" the engine all of the time. The Atomic 4 is rated at 30 HP at 3500 RPM. The torque is fairly constant over the speed range therefore the maximum HP at any RPM is proportional to that RPM (ie at 1750 RPM, max HP is 15). If it takes say 12 HP to drive your boat at a cruise speed of 1300 RPM, the engine is working very hard with the cylinder pressure just about at maximum. What this all results in is heavy duty wear and tear on things like rings and bearings. The easy solution is to get some pitch off of the prop and let the engine turn up faster. In the case of my Tartan, I installed a 12 x 5 and cruise RPM jumped from 1300 to 2000. (I think a 12 x 6 is probably the best choice) For the same hull speed, you are still putting about the same HP into the water (there may be a small efficiency issue but it is not a big deal) but now the engine is producing it at half again the RPM. You have lower cylinder pressures, better oil flow, better cooling flow, higher alternator output and plenty of reserve power (Wide open throttle approaches 3000 for the really rough going.) The only downside is the increased speed will give you more vibration especially if you have an alignment problem or a bent shaft. Putting the engine on rubber mounts should help that. A good prop shop can repitch a prop 1" either way assuming it has not already been repitched. You may want to try reducing the pitch 1" just to see the effect.

Subj: Regarding:Cruising design Prop Date: 96-10-20 12:51:15 EDT From: SFC GRIFF

The problem is that with the greater reverse thrust, there's also greater prop-walk, so the stern just kicks sideways faster. Unless you've got a huge rudder, and then you'd need a non-feedback wheel to control it, the boat's gonna be difficult to steer in reverse. That's why some have gone to twin screws, with the attendant problems. SFC GRIFF AOL Sailing Forum Consultant You should be able to run your engine at full recommended rpm's as stated my manufacturer. If engine can't get up there, you need less pitch or diamaeter, start with 1" less of either for about 200 rpms until yoyu can meet the number. Opposite applies if your engine runs faster than recommended speed. Increas pitch or diameter. the you will usually run (cruise) at 80% or whatever they recommend.

Subject: Re: A4: Prop by Cruising Design From: Tom Dove ( Date: Sat, 19 Oct 1996 15:05:44 +0000

I called Cruising Design about this prop, and they said it is 12x7, which my Atomic Four will not turn to a reasonable speed on my Ranger 33 (it has plenty of work with a 12x6 and prefers a 12x5).

On a boat with less efficient water flow over the prop than mine, it might be correct, but there's no such thing as a correct prop for a specific engine, without including a lot of variables about the boat, including displacement, keel configuration and cruising speed. I've seen Atomic Fours correctly propped with everything from a 10x8 to a 13x7. -- Tom

Qshicks: moter will develop 30 hp at 3500 rpm and 20 hp at2500rpm try crusing at 2800 rpm moter will like it and boat should reach hull speed with reserve for wind/ tide for a prop. call1-800-369-4335 which is michigan propeler for a free prop recomendition thay will want all of boats spec's plus moter spec's. Watch tip clearance to hull not less than 2 inches a grate prop book is propeller hand book by Dave Gerr

SAILSE32: I have a 1973 Ericson 32 and run a 12X6 prop with good results. I get about 6 Kts at 1800 RPM. If I had to select another prop I would go with a 12X5 to allow the engine to develop more RPM and therefore have more reserve power.

Subj: Regarding:Which tach to buy? Date: Sat,28 Jun 97 13:45:14 EDT From: LRZeitlin

First, let me confess that I really don't know much about the A4. Qshicks is the expert. But: The A4 was designed when there were only mechanical and relay tachs available. Mechanical tachs use a drive from the camshaft and are driven at half engine RPM. They usually are fitted with a square socket which accepts the 1/8" square tang on the end of the tach cable. The tach head is a mechanical speedometer which is calibrated in RPM. There are a number of makers of mechanical tach heads and they are available in auto parts stores. Stewart Warner makes a variety of heads, cables, and accessories to fit just about any mechanical tach. Of course it would be simpler to get an electronic tach since running wiring to the control panel is a lot easier than running a tach cable.

Subject: Re: tachometer problem Date: 08 Aug 1997 00:52:58 EDT From: MCPapa58

It gyrated wildly in over a 5-10,000 rpm range as I accelerated. At idle it ran at 500 rpm, but as I gave it gas the needle would start vibrating wildly as it accelerated. I bypassed the + and - wires and wired it directly to the btty. I ran a new wire to the tach from the coil. Didn't make any difference. I ended up going down to Shuck's with the old one and they gave me a new one that looked the same more or less. I put that in and the needle settled right down like it should. My mechanic (who I guess maybe isn't that good) didn't know what would have been wrong with my old coil that the engine would run fine yet it would effect my tach. Any ideas?

Subject: Re: tachometer problem (cruising design prop) Date: 07 Aug 1997 19:00:56 EDT From: CptnRn

I'm dieing to hear how the prop performs. Do you get any noticable increase in thrust in reverse (as claimed by the manufacturer)? Does it help in backing from a dead stop? What is your opinion?

Subject: Re: tachometer problem Date: 08 Aug 1997 00:57:50 EDT From: MCPapa58

Not having a working tach until now I can't say how good the prop is. I ended up putting a new coil in and the tach works fine now. I don't know why my engine would work fine but it would effect my tach. When I put some hours on the engine and can more readily monitor my fuel usage I'll put another post on the subject. After just running it one afternoon it seemed that I was able to make hull speed with a lower throttle, but as I said it's too early to tell. As for reverse, I've only had to reverse twice since it came back in the water, so I don't really have an opinion yet. I'm hoping I can cut down my fuel usage from 1 gal/hr to 1/2-3/4, it would increase my 12 gal tank' range.

Subject: Re: tachometer problem Date: 08 Aug 1997 09:19:10 EDT From: JAXAshby

If you are burning a gal per hour of fuel with your A4, suggest you pull back a bit on the throttle. Two reasons, 1.) while you'll cut down your speed by maybe 1/4 to1/2 to 3/4 kt, you'll extend your range by maybe 30%, 40%, or more, and 2.) while the A4 is a solid engine, it will run a LOT longer putting out 12-15 hp rather than 25 hp. An engine will usually get its best effeciency at max torque rpm rather than max hp rpm. Also, [personal remembrance, which may be wrong] I think hull drag increases as the cube of speed [I know this is true of airplanes]. That means a boat making six knots requires 8X more horsepower to drive it than the same boat making three knots. Note: a decent rule of thumb is [for a well tuned, good condition engine] an air cooled two-cycle gas engine will put out about 12 hp per gal of fuel burned per hour; water-cooled two cycle or air-cooled four cycle [gas] = 16 hp/gal/hour; water-cooled four cycle [gas] = 20 hp/gal/hr; and water-cooled diesel = 24 hp/gal/hour.

Subject: Re: tachometer problem Date: 09 Aug 1997 23:45:30 EDT From: LRZeitlin

JAXAshby, Your engines must be more efficient than mine. I was taught that a normal 4 cycle gasoline engine burns about .5 lb fuel per hp per hour. Since gasoline weighs approximately 6 lbs/gal, this means that the engine should put out about 12 hp/gal/hr. As a rule of thumb, most 2 cycle outboarders calculate that they get 10 hp per hr per gallon; a specific fuel consumption of .6 lbs/gallon/hr. Most diesels burn about .35 lbs fuel per hp per hour under ideal conditions. Diesel fuel weighs about 7 lbs per gal so the diesel would put out about 20 hp per gal per hr. I kept a careful log of fuel consumption on a Perkins 4-107 on a 1200 mile ICW trip. We averaged 6 kt and burned .82 gal/hr. My boat takes about 13 hp to reach 6 kt, so our specific fuel consumption was about .43 lbs/hp/hr. You are right about the power increasing as the cube of the speed, at least below hull speed of a displacement boat. It takes approx. 2.6 hp to move my boat at 3.5kt. Doubling the speed to 7 kt. (hull speed) takes about 21 hp. - Larry

Subject: Re: tachometer problem Date: 10 Aug 1997 08:54:44 EDT From: JAXAshby

Larry,I defer to your knowledge about specific fuel consumpsion figures. My figures came from a variety of third party sources over the years, i.e. enthusists magazines, spec sheets for various engines, eye-ball experience, etc. Sources that certainly may not be rigorous. Much was written about engine/fuel efficiency during the first oil crisis in 1973. Some of what was written may have been unduly optimistic. Certainly, what was written concerned engines designed for max hp rather than lowest pollution, running under the very best of conditions, and running at max torque rpm. (Let me make mention, though. The fuel supply in an airplane is definitely limited and the distances flown can be long. Fuel consumption is closely monitored. 16 hp/gal/hr is about what we consistantly got from air-cooled, four-cycle airplane engines at cruise [75%] power [assuming the engines were capable of manufacturer's full rate hp, which they may not have been)]

I still think [I may be wrong] that 1gal/hr through an A4 is pushing it. Maybe because on my 33 foot long 11'6" wide (supposedly) 12,000 pound boat I burn about 2/3 gal/hr (maybe a little less) to make about 5 kts (when the hull is clean).

Subject: Re: tachometer problem/fuel consumption Date: 10 Aug 1997 12:38:28 EDT From: LRZeitlin

Specific fuel consumption is a pretty fuzzy topic among engineers, primarily because there are so many different ways of measuring horsepower. Typically American manufacturers using the SAE guidelines rate engines, stripped of all power consuming accessories and without a muffler, on a test stand, working into a dynamometer, at full throttle, at various speeds including maximum torque RPM. This gives the highest possible HP readings and the lowest specific fuel consumption. With modern variable valve timing, high compression, lean burn, stratified charge, etc. I've seen specific fuel consumption figures as low as .4 lbs/hp/hr. This is in the diesel range.

European manufacturers using the DIN or CUNA specs, rate engines as normally accessoried and get higher specific fuel consumptions. Perkins says that the specific fuel consumption of my 4-107 diesel is about .34 lbs/hp/hr at 70% power. The Perkins is a rather conventionally designed engine, so that's about par for the course. I've seen adds for larger industrial diesels that get the fuel consumption down to as low as .32 lbs/hp/hr at most efficient operating speeds.

Air cooled aircraft engines are not particularly high tech as far as specific fuel consumption goes. For obvious reasons aircraft engines are optimized for reliability and high power output per pound, rather than for minimum fuel consumption. Air cooling does not permit the precise temperature control required, and the construction is rarely massive enough to permit really high compression. The 16hp/gal/hr figure may be about right for an engine on a test stand but probably is optimistic for a fully accessorized engine in an airplane. You can't fool the laws of thermodynamics. - Larry

Subject: Re: tachometer problem Date: 10 Aug 1997 14:34:44 EDT From: Qshicks

Many A4 owners report 3/4 gall fuel useage based on total hours run and total fuel bought so the 3/4 seems about average for most users qshick

Subject: Re: tachometer problem Date: 11 Aug 1997 09:25:17 EDT From: Bristol32

Mine burns about 3/4 gal per hour pushing a 13,000 lb boat in average conditions. Fact rather than theory.

Subject: Re: tachometer problem Date: 11 Aug 1997 11:28:54 EDT From: RHmpL33

I have a Pearson 30 with A4 with martec 12/6 prop. I used to burn 1 gal per hour in flat water (with a clean hull) at 85% of 'apparent' hull speed as indicated by a chart/plot that I made... rpm vs. Kts. The curve 'knuckled' at 6.4 kt @ 1600 rpm. This is my efficiency curve for maximum range.

I installed an adjustable mainjet and now I get 3/4 gph at 85% (1360 rpm) ---- You can calculate theory until the cows come home. My numbers are derived from the 'state of condition' for ***exactly*** this boat; and, I find it very practical ... because now I know precisely .....when to clean the hull, when to readjust the engine, clean the carb, etc. And in flat water, I know that I have 26+ hours before the next fill-up. KISS. :-) Rich

Subject: Re: tachometer problem Date: 13 Aug 1997 17:47:27 EDT From: LRZeitlin

Your results are right in line with theory. Your engine is developing about 10 hp at 1360 rpm, based on the specific fuel consumption. That should drive your Pearson 30 at about 6kt. and is a very efficient and comfortable speed to motor around. If you try to reach hull speed, a bit over 7 kt., you will double your fuel consumption. - Larry



A4 Transmission Adjustment

by Ron Davis

Note 1: This is harder to explain than it is to do. Don't hesitate to do this yourself. The reversing gear (transmission) is very hardy, they hardly ever go bad and usually just need a little adjustment.

Note 2: terms such as port, starboard, fore and aft assume the engine is mounted in the boat with the flywheel facing forward, transmission on the aft end of the boat. This is not true on some boats that use an Aqua-Pak drive and the engine sits in the boat backwards.

SO, your prop doesn't turn or drive the boat forward? Diagnose the problem. Check your prop shaft first, with engine off and in neutral, can you turn the shaft just aft of the engine easily by hand? If not you could have a problem with the packing gland or cutlass bearing, a line wrapped around the prop shaft or excessive barnacle growth on the prop. If the water temperature allows, dive overboard and check to make sure your prop and shaft are clear and clean.

If the prop is clean but it does not engage or it seems to slip out of gear as you increase RPM's, you probably need to adjust the transmission (actually called a "reversing gear"). You may be able to see it slipping by watching the prop shaft spin (just aft of the engine). If it noticably slows down when you increased the engine throttle or rotates erratically it is slipping.

Check your linkage to make sure that is has adequate throw to put the reversing gear in forward and reverse. On the A4 you can feel the forward detent when you put it in forward gear, reverse does not have a similar detent, you just push the shifter linkage back until reverse engages, the reversing gear whines loudly when in reverse.

Transmission adjustments for forward and reverse are both below the transmission cover plate. It is a rectangular plate on top of the reversing gear, behind the engine block. Remove the four bolts from the corners of the plate and carefully pry up the plate. If you are careful you can reuse the cover plate gasket, the oil inside it is not under pressure so it doesn't take much to hold it in. Warning, the oil splashes around alot when the engine is in gear, so you must replace the plate before testing out the reversing gear adjustments or it will spray oil all over the place. Don't ask me how I learned this. The plate doesn't need to be tightened down for this testing, just set it in place with a two bolts keep it from slipping off, the bolts don't even have to be snug, just start them a couple of turns.

FORWARD OPERATION: When you remove the cover plate you will see the Reversing Gear Case Assembly. The forward end of it is a large metal drum, which is the reversing gear casing. Set into the drum on the aft end are the clutch disks with pressure plate, and extending aft from them are three curved pressure plate fingers, they rest on a tapered metal cone. When you move the transmission linkage you will see it move the tapered metal cone, which slides back and forth on the drive shaft. Shifting into forward pulls the tapered metal cone aft spreading the three pressure plate fingers apart, this applies pressure on the clutch disks (due to cams at thier forward ends). The action of the curved fingers slipping into the grove on the tapered metal cone is what gives forward gear the "detente" feeling. When forward is engaged the engine crankshaft, gear casing, clutch, tail shaft and propeller shaft are all locked and rotate together as a single unit. So the prop rotates as fast as the engine turns.

REVERSE OPERATION: In reverse the shifting linkage both frees the clutch plates and thru the flat metal reversing bar (on the top starboard side) it tightens a Brake Band around the outside of the reverse gear case to prevent it from turning, this forces pinion gears to turn the tail shaft (and prop shaft) in the reverse direction. In reverse, the tail shaft rotates OPPOSITE to the crankshaft, but at only 75% of engine RPM (1.33:1). The reverse speed of your prop is only 75% of the forward speed for the same engine rpm's, which is why you have to use a lot higher RPM's in reverse to accomplish a similar response from the prop. You will not feel a Detente when shifting into reverse, the reverse adjustment determines how large a neutral zone you feel in the shift linkage before reverse gear engages. You do not want this zone to be excessively large as it might exceed the range of travel in your shift linkage. You can tell when reverse is engaged because it makes a loud whining sound, this is normal.

FORWARD ADJUSTMENT: Make sure the transmission is in neutral (easy to rotate the prop shaft). DM recommends disconnecting the shifter linkage at this point but I did not find that necessary. Remove the cover plate and expose the reversing gear assembly. The three curved pressure plate fingers are attached at the forward end to a cast metal collar (the pressure plate). Rotate the pressure plate until the hex head metal retaining pin is facing up, it is half way between two of the curved fingers. The retaining pin looks like a small hex head bolt with a slot in the head. The bottom end of that bolt goes thru the pressure plate and extends into a slotted adjusting collar (staked collar).

Loosen the retaining pin until you can turn the adjusting collar. Make only small adjustments, they make big differences, adjust it one notch at a time. When I first tried this adjustment the collar seemed stuck, and gave way suddenly spinning several notches, I couldn't tell how many so it took alot of trial and error before I got it adjusted correctly.

Turn the ajusting collar one slot (notch) clockwise. Clockwise rotation tightens the clutch. If you turn it too far clockwise the shifter lever will require excessive force to put it in forward. Several people have reported that on thier boat the difference between the clutch not slipping and very hard shifting was only one notch.

Carefully retighten the retaining pin, making sure that it goes into a slot on the adjusting collar and GENTLY retighten it, it has a lock washer to keep it snug. People have been known to strip the threads or break the cast iron pressure plate where the retaining pin goes through it by over tightening this retaining pin. If the threads get stripped, it is possible to drill and tap a new hole in one of the other thickened sections of the pressure plate, each are 1/3 of the way around the plate.

Adjust the shifter linkage if necessary for the neutral position. Test the linkage several times to shift in and out of forward, you want to feel the detente, but the shifting should not be unusually difficult.

Reposition the cover plate to keep the oil in the transmission, then start the engine and test the prop for slippage. If it still slips, adjust the adjusting collar another notch and try it again. It usually doesn't take much to get it back into adjustment.

REVERSE ADJUSTMENT: After coming out of forward there should be a well defined neutral area (varies with linkage) before reverse engages. If the prop shaft does not reverse before you reach the limits of travel on your shift linkage, then you need to adjust the brake band tighter. If the neutral zone is not well defined or too small (the prop never stops turning) you need to loosen the brake band. This adjustment is done with the large 3/4" hex head Ajusting Nut (has large holes in each flat side of the nut) that is near the top port side of the transmission cover plate opening. Turning it clockwise tightens the brake band which wraps around the gear casing. Turn it only one or two turns before testing the adjustment. There is a retaining spring clip that holds the Adjusting nut in position after it is adjusted, the clip has a little metal finger that holds each side of the nut. The Adjusting Nut can be turned without removing the retaining spring clip but be careful to avoid breaking the clip.

Ron Davis

Transmission operation

by Richard Britton

The thing I like about the old low-tech A4 is that it is a fundamentally simple engine that is un-stressed and should last forever if you treat right and blow it a kiss when you come on board! The flywheel is bolted firmly to the end of the crank. Treat the engine on startup as you would for any other, including startup, which means that you don't rev it high until it gets oil pressure up and warms up. Up to something like 1000 RPM will not harm it in the meantime. Usually idle speed while warming up is slightly higher than the 500-600 RPM idle speed when warmed up.

I would, however, remind folks that there is a needle pilot bearing that locates the bearbox transmission shaft in the centre of the end of the crank. The only time it is stationary is when you are in forward gear, ,when the planetary mechanism of the tr. is locked up solid with the crankshaft - hence to revs are 1:1 when comparing the engine/output shaft speeds.

When the tr. is in neutral the tr. shaft remains stationary while the crank does its think. In reverse, the tr. shaft rotates OPPOSITE to the crank, but at only 33% of engine RPM, with the bearing thereby travelling much faster (1.33 times engine RPM) than even in neutral. This is why your reverse speed of your prop is only one third of the forward speed than when in forward and why backing the boat is so much harder to accomplish for a given engine speed. You have to rev the engine higher to get as much of a "bite" by the prop in the water - disregarding prop shape etc.

This pilot bearing is not a large bearing, but works hard in neutral and harder in reverse. While it should be fine if the motor/tr. is in forward gear (as it was designed to do), it is a lot tougher on the bearing and gearbox if used in neutral or in reverse for an excessive amount of time. This mechanism could be what your previous owner was referring to, rather than a "freewheeling flywheel". You should expect a lot more rumbling noise while in reverse, as the transmission engages the "spider", "idler", or planetary gears as well.

Best wishes,

Richard Britton, "Friendly Dragon" 1976 C30, New Westminster, B.C.



Request for help diagnosing engine: "A4 ran like a top on Sunday....A few hours later it cranked more than usual to start, but ran normaly once started. Idled and sounded okay."

Avoid overcranking the engine with the raw water supply valve open, with no exhaust to blow the water out it can flood back into the engine from the muffler being overfilled and cause very expensive problems....I know it happened to me last year.

((Boat sat for a day and now won't start! Cranks and cranks...makes sound like it WANTS to start, but doesn't catch. I've got a mechanic who's looking at it in a few days...could it be the coil...he seems to think it's electrical...?))

Electrical is one of the first things you should check. You need 3 things for any gasoline engine to run, SPARK, FUEL & AIR. Most of the time the problems will be with SPARK or FUEL.


Are you getting a strong spark at the plugs (and plugs clean), if so then the electrical is probably OK. However, a coil going bad may start fine but quit when it gets warm.

A friend with an A4 found that his engine ran fine after a tune up, but quickly deteriorated until it quite running when the point gap seemed to go out of adjustment. It turned out that his distrubutor cam had acquired rust spots and the roughness was wearing down the part of the points that is in contact with the cam, resulting in the points closing after awhile. He polished up the cam and it was fine.


With automobile downdraft carberators you can look into the throat to see if you are getting fuel delivered. You can't do this with the updraft carberator on the A4. After turning it over for a while you could remove a plug and see if it smells like gas. DOES ANYONE ELSE HAVE ANY TIPS ON HOW TO CHECK THIS. You can loosen the gas line from the fuel pump to see if you are getting fuel that far. It should squirt out in pulses when your turn the engine over. Hold a bottle over the end of the line to catch the gas. But you could still have a clogged carberator jet or other carb. problems.

AIR: Is the choke working? Check it visually. My A4 rarely needs the choke to start unless its real cold out or has been sitting along time. But the manual says that it needs to be closed to create enough suction on the jets to begin drawing fuel thru the carb.

If you put a hand over the end of the carb mouth when you turn the engine over you should be able to feel suction, the pistons drawing air thru the carb. If you don't feel that you could have a stuck valve. A sticky valve could cause what you described, if stuck open it can prevent the pistons from drawing air/fuel in thru the carberator.

Compression: hold a finger lightly over the spark plug holes to see of you sense any compression.


To: RKMosier A4 Trouble Shooting & Carburetor Problems

I just had a new experience with my A4 carberator this weekend that may be relevant to your problems.

Because of vacation (BVI), work load and extremely HOT weather (often over 100 degrees), I haven't gone to the coast (Texas Gulf) for about 12-13 weeks to check on my boat. So the engine hasn't been run in that length of time.

My goal this weekend was just to deliver "Mystic" to the boat yard 6 miles away for a bottom job, in preparation for cooler Fall cruising.

The engine would not start, not even a sputter. The carberator was brand new 1 year ago, so it was the last thing I suspected and I started trouble shooting the other systems.

Spark: Coil: Pulled the lead from the coil to the distrubutor, got a good spark off of the coil. Removed #1 spark plug, laid it on the block and turned the engine over, a good spark was visible, so the ignition system appeared to be working.

Compression (air): Put finger over #1 spark plug hole and turned engine over to verify both intake (suction) and exhaust (compression) strokes. A valve stuck open can short circuit either of these. Both seemed fine.

Short of checking every spark plug and every cylinder for all of the above, basic indications were that those systems were OK. That left the fuel supply.

FUEL: Fuel tank dip stick indicated tank was over 3/4 full, I try to keep it close to full to minimize water condensation. I changed the fuel filter in the spring so I didn't recheck it. Using the manual fuel pump lever I could feel the fuel pressure build up as I pumped. For the first several manual pumps you can feel the fuel being pumped. After 3 or so manual pumps the lever will feel dead, this is because you've pumped the pressure up as high as it will go, at which point the pump linkage takes up the pressure from any additional pumping.

Fuel to Carburator: I suspected a bad fuel pump as I have replaced about everything else that attaches to my 1975 engine. So, after placing several paper towels and a cup to catch any fuel spills, I loosened the nut which attaches the fuel line to the carberator. It leaked gas so I knew fuel was getting as far as the carburetor. The pump was fine (but I think I'll order a replacement anyway; 1975 was a long time ago for a fuel pump).

Carburetor: This was the last thing I expected to have problems with. Everything else seemed OK, so by process of elimination, this had to be it. Reluctant to remove it, I first tried draining fuel bowl, to see how clean the gas was. My old Zenith 68 carb. had a separate fuel bowl drain plug, that allowed you to remove water and junk that settled to the lowest part of the bowl. This "replacement" Zenith 68 carb doesn't have that drain plug, but the plug you remove to get at the main jet serves almost the same purpose. Which tells you something about where the main jet is located. Hint: it is at almost the lowest part of the fuel bowl, so any junk that gets into the fuel bowl will end up at the main jet.

The fuel that drained out looked clean, so I replaced the plug. Where it is located I couldn't see into the plug opening, but in hind sight I probably could have inserted a screw driver and removed the main plug without removing the entire carburetor.

Hoping that this solved the problem I pumped up the fuel pump and tried to start the engine. The engine would start and run at lower speeds (up to 1/3 throttle) as long as the choke was closed. Above that it died. Open the choke and it died.

I read and reread the "Owner's Manual" description of how the carburetor works. This convinced me I still had carburetor problems. The Carb has an "Idle System" and a "High Speed System" It seemed clear that the "Idle System" worked as long as the engine was choked, and the "High Speed System" didn't work at all. Both are fed by fuel from the main jet.

Back on my knees, I removed the carburetor, careful to avoid damage to the intake manifold gasket, and examined the carburetor. It looked ok, so I removed the main jet plug, and sure enough, without removing it I could see it was clogged. I took it out and found a needle to clean it with. The Main jet (brass) was almost completely covered with a pale green slightly crusty substance (corrosion?). The hole in the jet was almost completely full of the stuff and some pretty good flakes had to be scrapped off of the surface. I cleaned it as best I could and replaced it, put everything back together. Since I didn't have a replacement carburetor gasket I decided to see if it would start before I took the carburetor apart any further. Guess what? The engine started and ran fine.

So in less than one year of use, the main jet on a brand new carburetor had become clogged with ? corrosion or what? I have an older spare carberator I'm going to rebuild and install in lieu of this "new" one. Then I will rebuild it and see what else I can find. Lessons learned. In the past I've experience intermittent sputtering at high speeds, sometimes "pumping" the throttle or partially choking the engine cleared it up. This is probably because something was partially clogging the main jet, and changing engine RPM's or the additional suction from the choke helped clear the main jet. Ron



The Owner's manual, p17, on my web site have the instructions for resetting the timing from scratch. It is not difficult.

Essentially you rotate the engine by hand until the #1 piston is at top dead center (TDC). You can tell when this happens by using a screw driver blade straight down into the #1 spark plug hole. As the piston rises you will be able to fill it with the screw driver and when it gets to the top (TDC) and starts to go back down you will be able to feel it and know that you just passed (TDC). You might have rotate the engine past TDC a couple of times until you get it right.

The points should just start to open when the #1 cylinder is at TDC which is also ONE of the times when that pin on the crankshaft is aligned vertically. If you turn the cranshaft another180 degrees until the pin is once again aligned vertically, the #1 cylinder will be at bottom dead center.

If it is out, put the distributor back in the engine and set the distributor cap in place. The position of the spark plug wires will tell you approximately which way the cap should be facing. The wires take on a set from heat and sort of hint at which way the cap should be oriented. The wire won't let you turn it much more than 1/4 turn one way or the other. This gets you in the ball park.

NOW, remove the cap and look where your distributor rotor is pointing. It should be pointing at the spark plug post on the distributor cap which runs to the #1 spark plug. If it is not, then note which way it should be pointing so that it would point at the #1 post. Lift the distributor up until you can rotate the rotor. As you lift the dist. the rotor will turn slightly, note which way it turns and how much. Rotate the rotor until it points approximately at the number 1 spark plug post on the distributor capl, allowing for the rotation you noted above and lower the distributor back into place. As you lower it into place, it will rotate the opposite direction from what you noted when you lifted it up. If it is not pointing close to the #1 cylinder post, try it again.

Once you get it pretty close, rotate the distributor base until the rotor is pointing directly at the #1 cylinder post. Then rotate the distributor slowly counter clockwise until the points just begin to open. That is it! The points should just start to open when the #1 cylinder is at top dead center.

The timing should be close enough to start the engine at this point. It is recommended that you use a timing light for the final timing.

CANADA - Robert Hess. Sells rebuilt engines, parts and accessories Atomic Four Engine Service, 5017 Mariner Place, Delta, BC, V4K 4J4, Canada Telephone: 604 (868-6646) email:

This web site has an excellent history of the Universal Motor Company and the design of the Atomic Four engine. I thouroughly enjoyed reading the information provided there. Robert Hess also provided some information that seems so important to Atomic Four owner's that I'm reproducing it here. His business is rebuilding these engines so I think it is prudent to listen closely to what he has to say. It has inspired me to go out and buy a timing light.

etting the ignition timing by adjusting the distributor while the boat is under full power ("power-timing") can sometimes result in excessive ignition advance, which can contribute to head gasket failure (or worse). Pre-ignition and detonation (knocking) caused by excessive ignition advance or high compression can cause head gasket failure, cylinder head combustion chamber damage, piston crown collapse, piston compression ring and ring land breakage, valve face failure, and connecting rod bearing damage. Poor grades of gasoline (usually found in third-world countries) with octane ratings below 89 make lowering the compression ratio through the use of two gaskets more important in order to reduce head gasket failure or other damage. Although leaded fuel was originally designed to reduce engine valve seat failure as well as raise gasoline octane rating, especially in engines such as the Atomic Four which do not use hardened (Stellite) valve seat inserts, the use of unleaded gasoline in the Atomic Four does not normally cause any damage to valve seats as long as the valve clearance is properly adjusted and stock valve springs are fitted. For that reason it is considered more beneficial to add octane booster when the fuel octane rating is below 92 than it is to add a lead additive to unleaded fuel.))

From: "Hess" To: Subject: Re: timing mark?

#1 cylinder is closest to the flywheel, and the pistons are numbered consecutively from there back: 1, 2, 3, 4. The correct static (engine not running) ignition timing is 0 degrees, and so the points should just OPEN (the coil produces the spark when the points open, not when they close) when the piston of each cylinder has just reached the very top of its compression stroke (both valves closed). The pistons of #1 or #4 cylinders go up and down together, and happily, the split pin for the hand crank tool in the end of the crankshaft points up and down when the pistons of #1 and #4 cylinders are at top dead centre and bottom dead centre (full up and full down). This is handy, because it can be used as an indication of crankshaft and piston position for setting the ignition timing. Later engines had a timing mark in the top of the hole in the flywheel cover, and so the split pin points at it when the pistons of #1 and #4 cylinders are at the very top or very bottom of their stroke. If you paint one end of the split pin you can use it to indicate when the pistons of #1 and #4 cylinder are either up or down.

Once the points gap is set to the correct gap using feeler gauges or a dwell meter (a dwell meter is much more accurate), the ignition timing is adjusted by loosening the distributor clamp cap screw and turning the distributor. Because the centrifugal ignition advance does not begin to advance the ignition until around 750 rpm, the ignition can be adjusted to the 0 degree timing mark while the engine is running using an automotive timing light as long as it is idling at less than 600 rpm. If you mark the flywheel cover with degree marks up to about 20 degrees on the left (11 o'clock) side of the 0 degree timing mark, you can use a timing light to set the ignition timing at the full ignition advance setting of 17 degrees before top dead centre (BTDC), which is reached when the engine is running over approximately 1,500 rpm. This setting is more important than the idle setting, because it is the full advance setting which directly effects cruising speed fuel consumption and power. Excessive advance can cause overheating, pre-ignition, damaged pistons, burnt valves, and/or blown head gaskets.

You can also check that the centrifugal ignition advance is working using a timing light by slowing the engine to around 600 rpm and then speeding it up to over 1,500 rpm while pointing the timing light at the timing marks. The timing should advance gradually from 0 degrees at 600 rpm, to about 9 degrees at 800 rpm, to 17 degrees at 1,500 rpm as the engine is speeded up, and then retard smoothly back to 0 as the engine slows down. If the timing changes abruptly, the centrifugal advance is probably sticking, and if the timing is erratic and doesn't stay constant, usually either the points are dirty/burnt/oily or the distributor shaft bushing is worn. I hope this helps, Robert

From: Subject: Re: Coil still overheating


Another variable which could cause the coil to overheat is dwell time. What is the voltage across the coil terminals when the engine IS running ? Does it change significantly with rpm?

I believe for a conventional points ignition , no external resistor, it would be typically 4V (ie 30deg dwell on 12V ) I will check mine when next at the boat.

I assume you do not have at Capacitor Discharge (CD) ignition since in this case the coil acts as a pulse transformer and would not get very hot. For a conventional transistor ( pointless ) system the dwell angle could be altered by the transducer spacing from the rotor or a transistor reluctant to turn off.

Just a thought. Tom Oday 27 Wine Time

Date: Tuesday, August 10, 1999 9:16:37 PM

Subj: re: BAD COILS


Thanks for the update Steve, I too replaced my ignition with the ignitor just before my 1 week vacation on the boat. It ruined my vacation when the coil went bad first day out (no spare). I've puzzling over what kind of coil to replace it with. A "Friend" a few years ago advised me that I needed to replace my old coil with one designed for external resistor, which I did, which may be why it burned out. Its a wonder my points didn't burn out frequently before. None of the repair or maintencance manuals I have address what kind of coil to use.

When the coil burned out on my vacation I replaced it with another Ext. Resitance coil, which works, but I've been wondering for how long. Sounds like I better get the Internal Resistance type, and keep a spare aboard.

Fair Winds, Ron


Subject: BAD COILS


An update on discussions with John Featherman about coils overheating and failing when using the Ignitor electronic ignition system as my new coil did. John informed me Don Moyer discussed the issue with the manufacturer of the Ignitor electronic ignition. Part of the problem is that the A4 is only 4 cylinders and runs at lower RPMs as compared to 6 or 8 cylinder engines running at higher RPMs. The Ignitor also reduces dwell time as compared to the points and condenser. This means the coil fires less often in shorter "bursts" and thus builds up heat. Perhaps one of you electronics heads can explain the specific reasons for this, but it seems to make sense to me. I'll try to explain what was reported to me.

The manufacturer stands by their recommendation that an oil cooled coil with a minimum 3 ohm internal resistor is the correct coil to use and that is what Featherman supplied to me. To confirm spec on the coils Featherman is shipping, he and Moyer tested the 14 coils they had in stock. They found that 13 of them tested at just under 4 ohms of resistance. However one tested at just over 1 ohm of resistance, well below spec. Perhaps the one originally supplied to me was also under spec. John has indicated that in the future they will test all coils before shipping.

John is sending me a new tested coil as well as a 1 ohm external ballast resistor to try as an experiment suggested by Moyer and the manufacturer. The external resistor is to be installed in line between the Ignitor and coil on the + side (I think that is correct). It may reduce overheating, but it may also reduce performance. If it does kill performance, then I can remove the external resistor and use just the coil with internal resistor.

Long story made even longer, we hope I just got a bad coil. That's the way my luck usually runs with engines and that is why I prefer sailing. It will be several weeks before I return to the boat, but after installation, I will let the list know what the outcome is. Featherman and Moyer also asked I report back to them.

BTW, John Featherman was responsive, concerned and obviously he and Don Moyer were concerned about finding a solution to my problem. I appreciate the service and am willing to spend a few $ more for same. Steve Nichols, "Telesis" '80 NP30 MkII



Subject: Re: A4 Stuck Valves, May 25, 1998 11:23 AM From: Qshicks Try this befor you pull the head [1] do a compreshion test with a gauge with the cilinders dry note the readings then add a tea spoon of oil to each cilinder and re test if no change you can assume that the valves are stuck in the open position if thay are you can push them shut with a skiney screw driver that has had the tip [ abount 1 inch ] bent over at a 45 deg angel buy reaching throu the spark plug hole and placeing it on the top of the valve and taping the valve down gentily one at a time and then testing the compresion again when you have them up again i would suggest that you change the oil and give the motor the marvil mistry oil treatment and then change the oil again this should get you runing again if not it is time to do a valve job but since you stated that the moter is a reasent over haul and ran well till you added the led replacer it would seam that that the motor dose not nead a valve job hope this helps qshick



Captain Ron