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Occasional Misfire following rebuild

BobMoe

New member
4.3GL rebuild including: head rebuild, new: risers, manifolds, wires, plugs, rotor, cap, performed by a volvo penta shop.

Engine runs smooth, no vibration, good power, no leaks, sounds or smells. It starts instantly.

On acceleration before full temp I will get one "pop" misfire and possible a second one then it runs normally with full power and smooth operation.

shop suggests there could be some water remaining in system, as when engine failed last fall, the fuel system was not winterized normally.

I checked fuel in filter/separator and pumped from tank and it looks fine, no separation or foreign stuff.

Using generally 93 octane fuel and did add some dry gas.

The facts that it starts instantly, runs without any vibration and sounds great, have me wondering how to diagnose / elimiate the annoying misfire.

Thanks for listening and for any suggestions you forward.

Boat is a 1999 seaswirl 190 BR, operated in southern CT off a trailer.
 
Need to know if it is fuel injected or carb. On fuel injected my be a clogged Idle Air filter or your timing could be off. I have had problems with the crank sensor not spaced correctly also. I had similar issue and found timing had to be advanced to allow the ECM to set the proper timing.
 
This 4.3 GL has a carb, that seems to be working properly. Intermittent issues require patience to get to the actual cause.
 
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