83 johnson 15hp, new head gasket, strange comp numbers advice please?

dkonrai

Senior Chief Petty Officer
Joined
May 9, 2009
Messages
719
long story short
replaced tstat and head gasket
glass sanded both sides of the head and water jacket
cleaned all crud off head and piston.
ran the motor for about ten minutes to check cooling and leaks.

checked compression:
hand pull, 6 strokes 115/115
use a drill, 130/140.

why the big difference between pulling and using a drill at low speed (poor mans starter), should i have concerns that i have a 10 psi difference between the two? i know about the 10 % rule, or 13 psi diff. i just am a little curious if i need to have any concerns?

before i replaced the head gasket the compression was 100/100.

thanks
dino
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,129
Re: 83 johnson 15hp, new head gasket, strange comp numbers advice please?

Compression looks good to me
Maybe the drill test had more oil on the cylinder/rings walls if you had done it after the handpull.
 

dkonrai

Senior Chief Petty Officer
Joined
May 9, 2009
Messages
719
Re: 83 johnson 15hp, new head gasket, strange comp numbers advice please?

Compression looks good to me
Maybe the drill test had more oil on the cylinder/rings walls if you had done it after the handpull.

thanks for the reply. never gave that a thought. makes sense. now i can sleep :)
dino
 
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