Bad Miss

Outlawzbasser

Recruit
Joined
Oct 5, 2024
Messages
3
I have a 1987 Johnson electric start 25hp motor. It's been sitting for five years, but I'm not sure of the total time. It was on a boat I purchased. I have it running with a bad miss. There is a confirmed spark on both plugs; it is getting fuel. A compression test showed 125 on both cylinders with less than 10% leak down. Will seafoam help? I'm looking for advice on the next steps.

Thank you
Outlawzbasser
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,746
Could be the classic lean sneeze.-----Open low speed mixture needle 1/4 turn.-----Or if motor sat with fuel the carburetor it might need cleaning.
 

saltchuckmatt

Commander
Joined
Jul 19, 2019
Messages
2,598
I agree, clean carb....I have 4 of these motors.

You can try to backflush the carb but taking it off is better.

Could be the lean sneeze that Racerone is talking about....easy to test.
 

Outlawzbasser

Recruit
Joined
Oct 5, 2024
Messages
3
After performing the carb rebuild and cleaning, the motor sounds great. So yes the carb did the trick. Some fine tuning to do once I get it on the boat.
 
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