115 compression

[dave1]

Looking at a boat that has a '91 115 Yamaha.. A mechanic looked at it and gave compression numbers of 115psi on cyl 1&2 and 120psi on cyl 3&4. The guy I normally use to look at my stuff says that the compression should be even on all cylinders. The engine seems to run well on the hose.. is this normal or should I stay away from this engine

[Ken]

Dave,
I think you are ok on the compression - as long as the cylinders are within 5 psi of each other.
If you do a shock treatment with SeaFoam or RingFree, those numbers could very easily come up a little, and may even smooth out.
The shock treatment, assuming one has not been performed on the 'ole Yammie recently, should bust loose some of the carbon buildup around the rings, and thereby, bring up the compression a bit.
Good luck [img]smile.gif[/img] ,
Ken K