WHat's a good compression to have on a 150 motor?

Looking at buying my first boat... So I need alittle advice.

Thanks

Depends on what motor, model, etc, they can range from 90 to 125.

Tex, take the boat and have it checked out before you buy it. Compression depends on the make and model, but differences between cylinders are equally important as absolute compression. Take a compression gauge and test it warm.

the absolute numbers will depend on age, make & model, who's doing the test, and how precise your gauge is. older motor expect at least 110. under 100 is generally cause for concern.

But the difference between cylinders is key - if the lowest isn't within 5% or 7% of the highest, walk away. how old is the motor?

warm the engine up, disable spark by pulling the emergency lanyard (or disconnect & ground the spark plug leads), screw the gauge into each hole, turn the engine over 3 or 6 times with the key, and note the reading. if you get a bad result the first time, do it again just to be sure.

the compression was 125 on all 6 cylinders. And it's a '90 mercury blackmax xr2 150...sound ok?

That is indeed good numbers on that motor.

have a dealer do a leak down test ,its a lot more accuate

great... thanks for the help