Mercruiser 165 mis-fire and compression check

S

Spare_Time

Cadet
Joined
Jun 25, 2008
Messages
21
last boating season I had carb issues. Long story short the marine mech. i took it to eneded up giving me a completely rebuilt carb. Get the boat on the water and carb runs nice except i now have a mis-fire that wasn't there. OK, i figure its ignition since the old carb with problems probably masked the mis-fire. Finally get to looking at the issue a few weeks ago. I start by doing a compression check and my numbers are wacky. The engine is 1987 Mercruise 165, 4cyl. (same as the 470). I think this eliminates the electrical problem I thought I had...

cyl 1: 140 psi
cyl 2: 90 psi
cyl 3: 110 psi
cyl 4: 110 psi

any thoughts as to what my next step is? Im not an experienced mechanic but know how to work on engines...should I oil up the cylinders and retry? What does this sound like? I hope I don't have to replace rings...

thanks!
 
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