johnson motor

[ringofish]

Heres one for ya lads, just bought a 1986 15hp johnson from a deceased estate. Ran fine first few times then lost power and stopped, now has spark on both pots but only runs on bottom cylinder. If I put the plug in the top it fires but wont run, take out top plug and runs pretty rough though.Any ideas would be great !!

 

[joereeves]

On those 9.9 and 15hp models, I've found that having the carburetor set slightly too lean will cause one cylinder to drop.

If you have compression and spark that will jump a 7/16" gap with a strong blue lightning like flame, look into the carburetion.

NOTE: The spark must jump that 7/16" gap as noted... simply jumping a spark plug gap just doesn't do it!