A proper compression check

[zonaman]

I'm looking for a boat and while I've done a few compression checks on autos, I'm wondering if there's anything special to remember when doing it stern on drives and outboards? Lowest cylinder shouldn't test lower than 80% of highest, right?

Thank you.

 

[180shabah]

Re: A proper compression check

Same as testing on a car, but run the bilge blower.

 

[JustJason]

Re: A proper compression check

close.... merc states that the lowest can be no lower than 70 percent of the highest. With no cylinder being no lower than 100 psi minimun

 

[Coors]

Re: A proper compression check

Wonder why Merc lowers their standards.

 

[Don S]

Re: A proper compression check

Merc didn't lower their standard, GM did. The same service bulletin hit Merc and Volvo at the same time, and both posted the process word for word.

Here is the Merc bulletin, I would post the Volvo, but don't have it so you could compare.

http://www.boatfix.com/merc/Bullet/97/97_25.pdf