70 hp Johnson Compression ???

pburchett

Cadet
Joined
Jul 23, 2002
Messages
19
What would the compression on a new 70 hp Johnson or even a fresh rebuild be? Wanted to compare the numbers with my 1988 Johnson. Have not performed the test yet, but I just wanted to know what to look for
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: 70 hp Johnson Compression ???

Expect healthy numbers to be over 100 and closer to 130-135 on that engine.Make sure all three are within 10% or closer.
 

slow-n-ez

Recruit
Joined
Mar 19, 2005
Messages
2
Re: 70 hp Johnson Compression ???

I have an '89 and it has 120 written on each of the cylinders. Hope that helps.
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: 70 hp Johnson Compression ???

I like to see the 49-cube OMC triple numbers in the 130+ range. They're designed as a fairly high compression engine. My '79 Stinger 75 still punches the gauge to about 145psi top to bottom. <br />- Scott
 

pburchett

Cadet
Joined
Jul 23, 2002
Messages
19
Re: 70 hp Johnson Compression ???

I'm getting a very small variation of 140 psi on all cylinders,<br />1=142<br />2=139<br />3=140<br /><br />or at least that is as close as I can read the gauge.<br /><br />I know the boat has been used very little and you can tell the starter has some resistance on it as it tries to turn the motor over initially. I found a pull rope for the motor so I thought I would give it a yank just for fun… made me realize how big of a man I am not.
 
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