1988 25hp dropping one cylinder at low speed

[BTL]

E25RCCA

Been having this little quirk for a while. Engine starts on the first pull and runs perfectly with the throttle opened up, but once I drop down to "no wake" speed, the bottom cylinder will sometimes stop firing and I just putt-putt along on one until I throttle up again. Both coils and plugs are brand new. The engine is still very useable, but I'd like to stop this before things potentially get worse.

Does this sound like a power pack issue?

 

[jimmbo]

To me it sounds like a wire from the Armature Plate either opening, or is chaffed and is grounding out as the timing retards and the wires flex

 

[flyingscott]

Agree You have the UFI ignition and all the wires are under the flywheel.

 

[racerone]

Well ----I looked at the 88 model and it does not show UFI for 88.------But I suppose a different year powerhead could be installed.-----Perhaps there are issues with fuel pump diaphragm or lower crank seal.

 

[BTL]

Hmm, if this symptom could be caused by a lower crankcase seal failure then that is definitely a possibility. I replaced that seal last year when I was installing a new exhaust housing. I wouldn't rule out that something wasn't seated just right. Seems odd that it would only happen at low RPMs though.

 

[racerone]

Post # 1 did not mention a new seal on the crank.-----Run with a timing light and see which cylinder looses spark at idle.-----And powerpacks are cheap / easy to replace / often fix all kinds of problems with a new one.----If not you will have a good spare on hand.------Factory parts or some online purchase delivered to your door ?

 

[BTL]

Just thought I'd update this in case anyone else has this problem. The next time I took my boat out the engine started vibrating a lot and was not running well at all on my ride back to the dock. Turns out two of the lower mounting bolts holding the powerhead were gone (don't know how I didn't notice this before) and another was loose. The exhaust tube up inside the housing was also very loose so I had to pull the powerhead to get all that hardware tightened back up. Don't know how all these bolts came loose since most of them were torqued down with lockwashers.

Anyway, I reinstalled everything with threadlocker so hopefully this doesn't happen again. Oh, while I was doing this I also noticed the water jacket was leaking around the plugs, so I went ahead and replaced that gasket along with the head gasket and thermostat just cause I already had it apart.

Thanks for the help!

 

[Willyclay]

Thanks for the update but how does it run now?

 

[BTL]

Runs great.

 

[Willyclay]

Great news!!