Normal Compression

rpeeples

Seaman Apprentice
Joined
Apr 3, 2002
Messages
47
My motor is a 1989 Mariner 40HP Oil Injected. <br /><br />I was wondering what the correct compression rate is for the cylinders?<br /><br />Thanks. :D
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Normal Compression

Howdy, Russell.<br /><br />There isn't a "correct" compression. There is a range: about 90psi to whatever.<br /><br />What is most important about a compression check is that the cylinders all come within a 15% range.<br /> :)
 

rpeeples

Seaman Apprentice
Joined
Apr 3, 2002
Messages
47
Re: Normal Compression

I guess I should have put this in the first message but, my mechanic checked both cylinders and said they were showing 125psi. He said that was good for the motor...
 

LOLHJ

Seaman Apprentice
Joined
Jan 19, 2002
Messages
46
Re: Normal Compression

im assuming that is perfect compression. my '86 mariner 30 hp also shows 125 on both cylinders.
 
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