newby with 25 HP johnson ????

[evand]

hows it goin guys? im new to the forum but not to boating.... i just picked up a 1992 johnson 25hp for my 68 princecraft speed boat. and i seem to have a wierd problem. it is only runing on one cylinder... but it has spark fuel and comp..... if its idling i can pull the top plug wire and it will make no dif, in how it is runing, i switched the coils and got the same result on the top hole, so that tells me its not the coil, and like i said its getting spark. and the plug is wet with fuel. i also put new plugs in....


any help would be great.


thanks
Evan

 

[BonairII]

Re: newby with 25 HP johnson ????

That cylinder NEVER runs? Or it quits firing after motor gets warm? Did you try a new plug(s). If plugs are wet...your running too rich and fouling the plugs.

 

[evand]

Re: newby with 25 HP johnson ????

It seems like it didn't fire at all at a idle but comes and goes under a load, if in neutral I can rev it with both plug wires on but if I try to take off in the boat with the motor under load it has no power and won't rev. If I try to rev it in neutral with the upper plug wire off it will rev but not 100%, but idles the same with the top wire off or on, def. A wierd problem.

 

[Cofe]

Re: newby with 25 HP johnson ????

Get a open air gap spark tester at a auto parts store and set it to 7/16 inch. You should have a strong blue spark.

 

[lazyfish]

Re: newby with 25 HP johnson ????

I am not a boat mechanic,I had a 20hp merc at one time.I had the exact same problem you are haveing now.I took the flywheel off and tried points plugs anything I could think of to try.For some reason,I forget exactly why,I rebuilt the fuel pump and that was the problem.There was a part of the pump that let extra fuel get into the piston area.The fuel pump is connected to the motor so the diaghram moves in and out.It still pumped enough to keep it running but not good and did not run on one cylinder.I did just like you and would disconnect the plug making me think it was a coil or points or something else.This is the first and only time it ever happened.As crazy as it sounds you might try the same fix.This was a 69-72 year model.If you try this please reply and let me know how it turned out and as well it you get it fixed please let me know what it was to cause the problem.

 

[evand]

Re: newby with 25 HP johnson ????

just talked to a johnson tech. and he said its a 90% chance that its the carb. any one else got a idea?

 

[lazyfish]

Re: newby with 25 HP johnson ????

did you finally get your motor fixed,I am very intersted in what the problem was.

 

[fireman57]

Re: newby with 25 HP johnson ????

Pull your spark plugs and crank it over. If you see mist coming out of the spark plug holes then you can be sure that it is getting fuel. If you can't rebuild/clean that carb.

 

[lazyfish]

Re: newby with 25 HP johnson ????

did you find what was making your motor run bad,just wondering.