1978 Johnson back fires out exhaust

modesto

Cadet
Joined
Jul 23, 2010
Messages
6
My engine starts up and every few seconds it will backfire out the exhaust and eventually kill the engine. I changed the plugs and rebuilt the carb. I have it running lean a half turn out. Does anyone know what I should do next. FYI compression is 100 on both cylinders.
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,612
likely either a timing issue, or air/fuel mix (carburation). Fix depends on model as suggested above.
 
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