Compression Test 2001 115 numbers..should I be worried

[bebrown73]

I'm looking at purchasing a bay boat with a 2001 Yamaha 115 4-cylinder. The current owner says the engine has approximately 500 hours on it. The boat and motor appear in good shape, but the compression test performed during the last 100 hour service gave some inconsistent numbers. The left side cylinders have 133 and 130 psi while the right sides have 121 and 117 psi. Any thoughts on whether those compression numbers indicate a problem?

Thanks in advance!!!

[jonp]

Kind of odd how there is almost a 13% from one side to the other. 133 vs 117. Could as simple as carbon build up which sea foam or ring free may help. I would say this is a marginal difference but I think further investigation is needed before moving forward. Maybe another compression test or a leak down test...

[bebrown73]

Thanks jonp