2009 4 stroke 115 compression question

[Sushiholic]

I am looking at a boat with this engine. apparently 3 cylinders have the same compression and the 4th is slightly lower. the engine has 370 hours. is the uneven compression something to worry about ?
I did not write them down but I think it was 3 at 190 and one at 175

[robert graham]

The general rule of thumb is that each cylinder should be within 10% of the others.....I'd run at least 3 tests on each cylinder to try and establish an average for each taking into account for slight differences in test procedures....

[rodbolt17]

best rule with a 4 stroke is a LEAK DOWN test.
compression test is a teat on a boar hog on that motor.
I am currently working on an F80 that had 143 on #1 and 135 on #4 but number 4 was the one letting in the water due to a corroded head.
leakdown was 45% on 4 and 10% on 1.
and you could hear the air from the tell tale.

[madharchod]

you have a problem there as this cylinder sits right at the bottom so with a 15psi difference can suggest a leak or may be you re-do the test again

[rodbolt17]

I cant say if you have an issue or not.
I am saying a compression test on a four stroke outboard can be a tit on a tom cat.