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post #1 of 6 Old 01-08-2001 Thread Starter
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Atomic 4 Quits

We have a Newport 27 sailboat with an Atomic 4 engine (1976). With a 3 bladed prop 11 or 12" that alows the motor to spin about 2100rpms at 6.6 knots you can''t ever get above 2100 with this prop.

Anyway, the engine starts immediately, runs smooth except for the fact that the idle fluctuates between 600 and 2500rpms in neutral. Also, after running for awhile, sometimes 6 hours - 12 hours the engine quits and cannot be re-started for quite awhile perhaps an hour. This always happens at the absolute worst possible time. We almost got run down by a tanker in the entrance to Mobile Bay and had a interesting time getting into Perdido Pass against a 6 knot ebb when the engine quit. Needless to say, you don''t go far from the dock without getting your sails up immediately and knowing how to use them.

This engine is very well maintained. We disassembled and cleaned the carburator and wired out all the jets.

We''ve placed 2 fuel filters inline with the fuel system, we have a Borg Warner electric fuel pump that I believe is either 2 or 4 psi. We also have a fuel pressure regulator which regulates the fuel pressure to 1 psi. The cap, points and rotor have been replaced. It seems like every 10 or 20 engine hours we''ve replaced the coil thinking that it is overheating. With a new coil that has a ballast resistor, the old one did too. The points, cap and rotor always look like new inside.
We''ve gone over the wiring thinking there was a problem there. Now it just has a hot wired switch for on and a push button to spin the starter.

We are a wits end with this motor. We''ve had mechanics come out and they can find nothing
wrong with it. I''m considering trying a Pertronics unit in the ignition and a new Mallory oil filled coil as well as installing a fuel pressure gauge right before the carburator to make sure
that the fuel delivery is not wigged out somehow.Has anyone ever experience such a problem with their engine?

I''d really rather not put a Volvo MD2020 with a down angle drive in at the cost of $5500, but that may be the only way to make this problem go away.
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post #2 of 6 Old 01-08-2001
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Atomic 4 Quits

From your description you sound like you have all the "bases covered". I''d also suspect the coil (as you do) and would do a trial mounting of the coil on a bulkhead, etc. ... AWAY from the engine heat. Just because you replaced one coil does not mean that the replacement coil is any better !!!! If the system fails again I would do a complete primary and secondary ignition circuit analysis ... ***at the exact time of failure*** and not waiting until the engine cools down, etc. If you have the values of resistance, etc. beforehand you will have values to check and COMPARE immediately after the failure. (I''d also check the ground circuit from the engine to the battery for corrosion, high resistance, etc.)

You might also want to join and pose your question to the "Atomic-4 discussion group" here on Sailnet. Your described ''problem'' has been discussed there in great detail many times in the past.

hope this helps.
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post #3 of 6 Old 01-17-2001
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I ahve had a lot of experiance with this old work horse of an engine and I have never failed to get back home. I can relate one thing that you may have over looked with this engine. On my 1970 Bristol 29 I started to have the same trouble with the motor quiting on me after a period of trouble free running. I too checked out all the systems-fuel-ignition-coil,checking the spark. What I found out to be the problem was the exhaust system! I still had the original double walled copper tubbing. The Exhaust gasses exit by the inner pipe with the cooling water injected into the jacket around this pipe. the inner pipe wall failed and alowed the exhaust into the second jacket. In short this caused the pressure to build up in the exhaust system and the engine would slowly overheat to the point that the enigine would shut down do to temp.and back presure.
I replaced the exhaust system with a new water lift system and I never had trouble again. I now hav a 1977 C&C 36 with yet again the Atomic 4 as the power plant and I find this engine to be a very reliable power plant with the proper maintenance and upgrades that are now available eg. electronic ignition and a oil filter system installed.
I hope this may help
Good luck
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post #4 of 6 Old 01-19-2001
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AHOY.....That''s quite a game of Russian Roulette you''ve got going there buddy!! You sure you even want to mess with it??!?!??CHEESES!!! You can pick up another pieca tupperware at the Sea Scouts for a Beer and a song f''chris''sake!! GET REAL!!The boat isn''t worth it...gitabetterone.....Rev. Mike
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post #5 of 6 Old 03-08-2001
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If your idle varies that much I would suspect a fuel delivery problem or vacuum leak.
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post #6 of 6 Old 06-07-2001
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We had a sister engine that sounds like a cloned version of your troubles. I now is the best engine we have ever had as a mooring in the river. Upgrade or enjoy the sail.Big Red 56
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