1987 50HP Johnson missing at idle
Engine: 1987 Johnson 50 HP (J50TLCUD)
I've had a persistent problem of the engine missing at idle that makes me hesitant to take the boat out. The carbs have been professionally rebuilt, spark plugs and wires have been replaced, fuel pump, fuel filter and fuel/water separator replaced, and all fuel lines replaced. Could this be a flywheel or pickup problem? Coils? What should I check next?
Thanks in advance.
Check the compression.
Define the miss. Is it rough idle or coughing and sneezing?
txfour, it's both a rough idle with occasional coughing and sneezing
So,,,compression is good?
ChampioNman, we've had steady rain here for 2 days and haven't been down to the slip to check compression. Will do as soon as I get a chance.
ChampioNman, ran compression check today. 160 psi bottom cylinder, 165 psi top cylinder. The gap on the spark plugs was wrong, .030. Regapped to .040 and now purring like a kitten.
Champion QL77JC4 gapped at .030....not .040. Don't run any other type plugs as well(NGK ect)
Last edited by omcforever; 07-21-2018 at 02:56 PM.
Age and treachery will always overcome youth and skill !!
Originally Posted by omcforever
Champion QL77JC4 gapped at .030....not .040. Don't run any other type plugs as well(NGK ect)
My service manual says gap is .040.
The stickey above posted by Seahorse has updated recommended plugs for E/J engines.
If your running the spark plug that your OMC service manual has listed to run, and it shows gap at .040, and your motor is running great. Then that's what I would do. Now, you can run the plugs shown in the sticky at the gap shown and your motor should run fine. We used to gap the plugs in several motors at .040, depending on the motor and spark plug.
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