difference is compression

[medic2051]

just a general question, when looking for used johnson outboard what is an acceptable difference in compression betwwen cylinders?<br />Thanks

 

[DHPMARINE]

Re: difference is compression

3 points is nice,but seldom seen.Small HP no more than 10psi difference.V6 150 HP and up 15psi to 20psi More than that could be trouble.<br /><br />DHP

 

[reload]

Re: difference is compression

I don't like to see any more then ten in any cse even on automobile engines.<br /><br />Paul

 

[G DANE]

Re: difference is compression

I've got a V4 115 Evin 1991 I bought last year, didnt get it on boat. Shows 125 124 125 135. Hope to be ready at spring. Numbers taken with a half dead battery, slow crancking in winther. Hope it will be more even after a decarb. The one high worries me though.

 

[Dhadley]

Re: difference is compression

With Evin/John motors you dont want any more than 15 lbs difference between the high reading and the low according to the manufacturer. An actual number is not as important as the difference. If its a V motor make sure both heads are a matching set. If not, that may throw off the differences some.