Merc 150 1988 compression numbers

[Drew in B'ham]

I looked at a boat with the above motor, I like the boat OK but want to compression test the motor. One person told me the compression should be between 115 to 125 PSI and all cylinders within 10% of each other. Can anyone verify that please?

 

[Chris1956]

Re: Merc 150 1988 compression numbers

Hey Drew, If the cylinders are within 10% the motor is good. The actual compression numbers are not important, since we do not know how accurate the gauge is. Remember, if the cylinder compression numbers are all the same, the motor has not suffered any damage.