Have a buddy who is thinking about purchasing a boat. What are your thoughts on the following compression readings?

95
97
105
105
97
90

how old and what motor

They say to have all cylinders within 10-15%. I suppose he should be ok, but I hope he knows going in that it can blow any minute.

Test drive it then test it again bet it goes up.if not I'd pass

if it was an old straight 6 I'd say it had a warped head,..who knows.
22% difference in 105 to 90,...age and hours is always a factor..
and who done the test,..??

225 optimax w/ 700 hours.

Is there a scale in said boat?

I would be a little hesitant with the cyl showing 90 (assuming it's a quality guage being used)... Definitely get a leak down test done!! That's the only real way to find out the motors "health".

Should be in the 110-119 psi range.

Since you are asking, there must be some concern about that engine. Don't buy a boat you have "some" concern about. Once it blows, you knew better to begin with. But with that said, there are two types of engines...1) those that are blown, 2) those that are gunna blow.

I would buy it with the intent of freshening the motor.

Have him run it by a dealer for a leak down test. Often there is a ton of variance between compression gauge sets. The leak down being more accurate. Its cheap insurance. Spend $100 now to save $4000-10,000 later.

^^^^^ yep... And if those are the right numbers, I'm not buying that boat. That motor I headed for a rebuild.

this. plus 700 hours is a lot, but i had one that i sold with 932 and its still running to this day and he has around 1135 on it now. maintenance and service records

Yep...leakdown test...5 to 8% leakdown at max, anymore, I would reduce my offer substantially to compensate for freshening up.

Gman