85hp force compression

medic2508

Recruit
Joined
May 22, 2009
Messages
5
Hello again,
Think I may be getting close to having a boat but not sure. I bought a bayliner bowrider with a 85 hp force motor for 400.00. I was told by the owner that he had the motor checked and the mechanic told him it had good compression but needed a new starter. I bought a new starter and it did nothing but make sparks. Found that the shaft on the new starter was froze. fixed that problem tried starting it and it would barely crank with the plugs in. bought a compression tester and found #1 110, #2 50 and #3 40. Took the head off the head gasket looked good the cylinders were smooth and the pistons looked like they just had carbon build up. When I turned the flywheel # 1 would making a sucking noise when it passed the exaust valve but #2 and 3 did not. Did I get lucky enough just to replace the rings or should I replace the pistons and have the cylinders bored. I don't care about high performance I just wanted a cheap boat to take the kids fishing in and do some diving. Thanks for any help.
 
Joined
Jul 4, 2009
Messages
15
Re: 85hp force compression

I think something else must be wrong personally. My Force 50HP was only getting 35-40 PSI and had a good chunk of the piston burned, and rings were seized.

If the rings do not look worn-I would try a new head gasket and thorough decarbing before a ring and honing job.
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 85hp force compression

If you're really lucky, you may not even have to re-ring at all. The rings on 2 & 3 may just be froze up due to carbon. Try soaking those two cylinders with some de-carb treatment overnight. Seafoam or similar product. IF that doesn't make a significant improvement and cylinder walls are in good shape, then a quick hone and new rings may be all that is needed. To determine if pistons need to be replaced you need to mic the cylinders. Maximum wear is just over 5 thousandths of an inch. Anything over that would require new pistons.
 
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