Compression Check Numbers 9.5, 15, 25, 35Hp

T

Tom_C

Seaman Apprentice
Joined
Apr 11, 2009
Messages
30
I pick up a compression tester today to check my new to me 1982 35hp. As long as I had it I figure I test my other motors.

Are these numbers good?

1973, 9.5Hp 70psi both.

1981 15Hp 110psi both.

1982 35Hp 150psi top 160psi bottom.

1991 25Hp 115psi both.
 
E

EN2

Chief Petty Officer
Joined
Nov 19, 2007
Messages
404
Re: Compression Check Numbers

Re: Compression Check Numbers

These numbers look good, maybe do a decarb on the 35 and test again.
 
T

Tom_C

Seaman Apprentice
Joined
Apr 11, 2009
Messages
30
Re: Compression Check Numbers

Re: Compression Check Numbers

Thanks EN2, will do.
 
Mas

Mas

Lieutenant Commander
Joined
Oct 3, 2006
Messages
1,656
Re: Compression Check Numbers

Re: Compression Check Numbers

Tom_C said:
1982 35Hp 150psi top 160psi bottom.
Click to expand...

Within 10% of each other is the rule...you're OK. A decarb may even them out.

MAS
 
F

freddyray21

Commander
Joined
Jun 10, 2006
Messages
2,460
Re: Compression Check Numbers

Re: Compression Check Numbers

the 9.5 looks a bit low to me, but if it runs good then it may be fine.
 
jbjennings

jbjennings

Captain
Joined
Jul 18, 2007
Messages
3,903
Re: Compression Check Numbers

Re: Compression Check Numbers

the 35hp actually looks too high to me. I'm wondering if EN2 is suggesting a decarb to get rid of carbon buildup that might be decreasing volume in those cylinder heads and causing abnormally high compression, and that a decarb would solve?
Just wondering,
JBJ
 
tashasdaddy

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Compression Check Numbers

Re: Compression Check Numbers

the 9.5 is fine, rope start if you get 60 it is good.
 
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