My Atomic 4 engine will start well and runs well at low RPM's. When speeded up, or when the engine is put under greater loads the RPM's plateau and it gradually chokes and stalls. It wants to keep on running but eventually stalls. It will restart immediately. This issue has been there for a year (other fixes were tried last summer - renewed cooling system, water pump,etc)- but in the last three weeks I have had the ignition system upgrade to an electrical one; the gas tank cleaned out; the gas tank vent line cleaned and replaced; put new gas in; had the carb rebuilt; and the gas pump replaced (a new electrically one)- improving the engine's operation but not solving the problem. We have "sea tested" the enging with the mechanic on board making adjustments - he too is frustrated! Any and all help greatetly appreciated.
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Have you thought to check the valve
clearance on the engine? (intake and exhaust valves) The higher loads will cause more heat, the valve clearance may be lost due to expansion and you loose compression, the engine stalls, cools off, the valve clearance recovers and the engine restarts. That's my wild guess.
clearance on the engine? (intake and exhaust valves) The higher loads will cause more heat, the valve clearance may be lost due to expansion and you loose compression, the engine stalls, cools off, the valve clearance recovers and the engine restarts. That's my wild guess.
Atomic 4 Stalling
If you didn't have the needle and seat replaced when the carb was rebuilt that is the first place I would go. Does the engine keep running if when it starts to stall, you add a little choke? If this is the case then you definitly have a fuel/air problem.
If you didn't have the needle and seat replaced when the carb was rebuilt that is the first place I would go. Does the engine keep running if when it starts to stall, you add a little choke? If this is the case then you definitly have a fuel/air problem.
Anemic Four = Universal
Dear Bill, I have another job to go to, so am about to leave. I was debating if I should tell you this or not, the 'Darth Vadar' side won because when I asked myself if I would want to know the answer was an absolute YES! The Atomic Four was the 'second' worst marlized engine ever built. The nicknake "Anemic Four" is, i'm afraid, well deserved. Whilst deese guyssss sound right, go for the carburator, adjust the valves and so on. My advice is to kick over the table! Are keeping the boat? Will you, or can you see yourself getting into a somewhat 'dangerous' situation whence you will need a 'RELIABLE' engine? Then 1) use that one for a mooring, pretty good for that purpose. 2) stick a Yanmar (pretty bullet-proof) in there. or 3) Drop a Universal in they match up pretty good as a replacement to the A4 and I ahve heard nothing but good about them too. Now, now to youse guys who have 'reliable' A4's I say unto you, I too owned one, but I satyed right on top of it, and was really happy when I sold it. This fellow is already havin troubles, errr issues, and a diesel is so much safer. One more fact to consider: if you do not have a 'FIXED FIRE SYSTEM' inside that engine bay for that gasoline engine, the vessel is illeagal as far as the CFR'S are concerned (USCG LAW) and as such, if a fire originates there will NOT be covered by most insurance carriers. If you do keep the engine, install a 'FIXED FIRE SYSTEM'! Many older A4's do not have one but they are subject to the law. Don't kill the messanger here boys...;-)
Dear Bill, I have another job to go to, so am about to leave. I was debating if I should tell you this or not, the 'Darth Vadar' side won because when I asked myself if I would want to know the answer was an absolute YES! The Atomic Four was the 'second' worst marlized engine ever built. The nicknake "Anemic Four" is, i'm afraid, well deserved. Whilst deese guyssss sound right, go for the carburator, adjust the valves and so on. My advice is to kick over the table! Are keeping the boat? Will you, or can you see yourself getting into a somewhat 'dangerous' situation whence you will need a 'RELIABLE' engine? Then 1) use that one for a mooring, pretty good for that purpose. 2) stick a Yanmar (pretty bullet-proof) in there. or 3) Drop a Universal in they match up pretty good as a replacement to the A4 and I ahve heard nothing but good about them too. Now, now to youse guys who have 'reliable' A4's I say unto you, I too owned one, but I satyed right on top of it, and was really happy when I sold it. This fellow is already havin troubles, errr issues, and a diesel is so much safer. One more fact to consider: if you do not have a 'FIXED FIRE SYSTEM' inside that engine bay for that gasoline engine, the vessel is illeagal as far as the CFR'S are concerned (USCG LAW) and as such, if a fire originates there will NOT be covered by most insurance carriers. If you do keep the engine, install a 'FIXED FIRE SYSTEM'! Many older A4's do not have one but they are subject to the law. Don't kill the messanger here boys...;-)
Dirty emulsion tube in the carb.....
The emulsion tube ... that which is responsible for the vaporization of the fuel - about 1 inch long and has two holes drilled perpendicularly drilled into it is VERY susceptible to catching dirt. *Any* dirt at all in the emulsion tube will cause such symptoms. Second possibility causing such symptoms is a blown head gasket (usually between #3 & #4). When was the last time you retorqured the head studs???? ... should be done every year. Go to moyermarine.com, ask your question on that forum for other suggestions. BTW - when at that website, consider to get a copy of Don Moyers "Maintenance & Rebuild Manual" .. will be one of the best investments you can spend on keeping the venerable A4 purring like a kitten. Even if you are not handy with wrenches you can let your mechanic use the book to good effect as there are very FEW mechanics nowadays who understand the Atomic-4. Its a GREAT engine that with a little care will last for years and years. There are upgrades/'modernizations' available from the moyermarine website. Don Moyer is the world's "guru" of Atomic-4s. For reliability and a smoothrunning engine, **nothing** beats a properly maintained Atomic 4. You can ignore most of Capn Rons post ... mostly uninformed BS. My bet is either a dirty emulsion tube in the carb or a blown head gasket. Hope this helps
The emulsion tube ... that which is responsible for the vaporization of the fuel - about 1 inch long and has two holes drilled perpendicularly drilled into it is VERY susceptible to catching dirt. *Any* dirt at all in the emulsion tube will cause such symptoms. Second possibility causing such symptoms is a blown head gasket (usually between #3 & #4). When was the last time you retorqured the head studs???? ... should be done every year. Go to moyermarine.com, ask your question on that forum for other suggestions. BTW - when at that website, consider to get a copy of Don Moyers "Maintenance & Rebuild Manual" .. will be one of the best investments you can spend on keeping the venerable A4 purring like a kitten. Even if you are not handy with wrenches you can let your mechanic use the book to good effect as there are very FEW mechanics nowadays who understand the Atomic-4. Its a GREAT engine that with a little care will last for years and years. There are upgrades/'modernizations' available from the moyermarine website. Don Moyer is the world's "guru" of Atomic-4s. For reliability and a smoothrunning engine, **nothing** beats a properly maintained Atomic 4. You can ignore most of Capn Rons post ... mostly uninformed BS. My bet is either a dirty emulsion tube in the carb or a blown head gasket. Hope this helps
Atomic 4 does opposite
Well Bill, my rebuilt A4 only has maybe 15 hrs and it does the opposite. It ran good for the first couple of times then just started running bad, and I was only putting around the Marina. My mechanic told me it needed the carburator rebuilt because of bad fuel. So, I bought a new carburator and it ran good again until I went on a trip down the coast and motored for about 5 hrs straight, Now it does the opposite of yours, runs better at higher rpms but dies when I try to idle it. The mechanic says its bad fuel again and he might have to rebuild my brand new off-the-shelf $300 carburator. I'm beginning to agree with Capt Ron. Does this ever end? Everytime I go out and have to run the engine for any length of time do I have rebuild the carburator? Was the fuel that much better when these boats were made? I have expensive filters on it now and am adding fuel additives, gum out, lead substitute everthing the mechanic says, and he keeps saying like Rich that these are sturdy old engines and will run thru anything. Granted, the boat sat for along time before I restored it. Perhaps there is junk in the tank that got stirred up out in the ocean. He says keep running it until all the bad stuff gets run thru. Or until I run out of money for carburators.
Well Bill, my rebuilt A4 only has maybe 15 hrs and it does the opposite. It ran good for the first couple of times then just started running bad, and I was only putting around the Marina. My mechanic told me it needed the carburator rebuilt because of bad fuel. So, I bought a new carburator and it ran good again until I went on a trip down the coast and motored for about 5 hrs straight, Now it does the opposite of yours, runs better at higher rpms but dies when I try to idle it. The mechanic says its bad fuel again and he might have to rebuild my brand new off-the-shelf $300 carburator. I'm beginning to agree with Capt Ron. Does this ever end? Everytime I go out and have to run the engine for any length of time do I have rebuild the carburator? Was the fuel that much better when these boats were made? I have expensive filters on it now and am adding fuel additives, gum out, lead substitute everthing the mechanic says, and he keeps saying like Rich that these are sturdy old engines and will run thru anything. Granted, the boat sat for along time before I restored it. Perhaps there is junk in the tank that got stirred up out in the ocean. He says keep running it until all the bad stuff gets run thru. Or until I run out of money for carburators.
Diagnostic suggestions offered
Hello - I am not going to comment on the Atomic 4 love/hate thing but wanted to give some suggestions on how to troubleshoot your problem. I am assuming it is a fuel-related problem that may not be correct. 1. Install a outboard-engine type fuel primer in front of the main fuel filter. Pump it and see if the system pressurizes correctly - you may have an air leak somewhere and the electric fuel pump is much more sensitive to that issue than the older mechanical pump. 2. By pass the oil pressure shutoff valve, if you have one, to make sure that your fuel pump is getting electricity all the time. 3. Blow some air into your fuel tank (through the fuel intake) and make sure the intake is not plugged or worse corroded. 4. Finally, check everywhere for fuel leaks after your engine stops running. I am passing this advice along as I had a problem with my engine running 15 minutes and then stalling and after doing only some of the things that you have been through finally realized I had a leak at the fuel intake on top of the fuel tank. Once you have the engine running properly of course you will want to put the shut off switch back in the loop as well as possibly remove the pumper. Good luck!
Hello - I am not going to comment on the Atomic 4 love/hate thing but wanted to give some suggestions on how to troubleshoot your problem. I am assuming it is a fuel-related problem that may not be correct. 1. Install a outboard-engine type fuel primer in front of the main fuel filter. Pump it and see if the system pressurizes correctly - you may have an air leak somewhere and the electric fuel pump is much more sensitive to that issue than the older mechanical pump. 2. By pass the oil pressure shutoff valve, if you have one, to make sure that your fuel pump is getting electricity all the time. 3. Blow some air into your fuel tank (through the fuel intake) and make sure the intake is not plugged or worse corroded. 4. Finally, check everywhere for fuel leaks after your engine stops running. I am passing this advice along as I had a problem with my engine running 15 minutes and then stalling and after doing only some of the things that you have been through finally realized I had a leak at the fuel intake on top of the fuel tank. Once you have the engine running properly of course you will want to put the shut off switch back in the loop as well as possibly remove the pumper. Good luck!
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