70 HP Johnson compression test

[wetcoaster]

Just did a compression test on a 70 HP Johnson I picked up with a 16'
what is a good number? i got 85 psi on top and mid & bottom was 70psi
the motor is a '89 are these average for the year or should I be looking at new rings?

 

[CaptainHook]

Re: 70 HP Johnson compression test

I have a mid 80's 70 hp evinrude here. Compression is about 125 psi on each. As far as I have ever known (some may disagree, but I have always followed) once you get below 100 psi your getting border line on whether or not the motor is gonna run much longer.

 

[Lion hunter]

Re: 70 HP Johnson compression test

Are you doing it with a pull rope or starter? It's low if your doing by a starter, and they should all be within 10% of each other. There really is no magic number for compression. Certainly if your above 100 your good but it is more important that the numbers are within range of each other. Read the "Top secret" file at the top of the Johnson forum and do a decarb and then retest.

 

[wetcoaster]

Re: 70 HP Johnson compression test

Appreciate the advice, just checked the 'secret file' useful info. I didn't warm up at all, just cranked it over with guage in. I think a retry with warm engine is in order. Thanks again

 

[Markiemrk]

Re: 70 HP Johnson compression test

Are you doing it with a pull rope or starter? It's low if your doing by a starter, and they should all be within 10% of each other. There really is no magic number for compression. Certainly if your above 100 your good but it is more important that the numbers are within range of each other. Read the "Top secret" file at the top of the Johnson forum and do a decarb and then retest.

 

[Markiemrk]

What’s this top secret file and and how do I find it ? Also is A compression of. 138 , 130, and 138 good on a 2000 70 hp ?

 

[Markiemrk]

What’s this top secret file and and how do I find it ? Also is A compression of. 138 , 130, and 138 good on a 2000 70 hp

 

[saltchuckmatt]

Compression wise your great....not supposed to post old threads, just make a new one and post or copy things you've read.

 

[Markiemrk]

Compression wise your great....not supposed to post old threads, just make a new one and post or copy things you've read.

Ok , got it . Still trying to navigate this forum . I did post a new one with some other questions regarding the 70 hp motor .
Would you mind taking a look at it ?

 

[alldodge]

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