'87 Johnson GT150 Compression Question

[kmaglothin]

1987 Johnson GT150 - Initial compression test - Results - 100,100,100,100,103,95<br /><br />Decarbed engine - 100,100,96,98,96,95<br /><br />I know it is within limits...but...I am curious what things can cause compression to change 4 or 5 pounds like I got?

 

[DJ]

Re: '87 Johnson GT150 Compression Question

There are a lot of factors, such as:<br /><br />Position of throttle-open vs. closed.<br /><br />Temperature<br /><br />Amount of oil on the cylinder walls.<br /><br />Cranking speed.<br /><br />Another guage may give you a completely different set of readings. Don't look at the number value, look for the consistancy across the board.

 

[kmaglothin]

Re: '87 Johnson GT150 Compression Question

Thank you! I can see three of those that could have been the cause. I guess I should be happy with what I have considering the age of the motor.

 

[DJ]

Re: '87 Johnson GT150 Compression Question

Ranger,<br /><br />Those readings do not bother me. Another guage may show them all to be around 125, or better.