compression on my 85 Johnson 150hp low???

[bmurray]

well finally did the compression check on my 85 150 crossflow, and found it quite low. It was about 65-70 psi on all cylinders (didn't do test with throttle open). Now I will do the decarb. I don't think it has ever been done, and should be after every 50 hrs. I don't think this is going to bring it up very high, but we will see. Could this be a low compresion engine that was setup at 80 psi? Should I consider an overhaul? I want to do some head mods but need a solid engine before I start. If anyone has any input please reply. Thanks

 

[hondon]

Re: compression on my 85 Johnson 150hp low???

SOMETIMES,a nice soak in decarb, then a blast with a leakdown gauge, will break those rings loose.SOMETIMES.

 

[bmurray]

Re: compression on my 85 Johnson 150hp low???

update. with the trottle wide open and battery fully charged I'm getting 80-85 psi. I will decarb next weekend. Does anyone have any numbers before and after de-carbing. I don't think this motor has never been done in 18 years

 

[NathanY]

Re: compression on my 85 Johnson 150hp low???

That is kinda low but not bad. As long as all cylinders are within 10% of each other you will be good. Your readings will change after the engine is warm, and you decarb. More than likely going up.

 

[sterudpa]

Re: compression on my 85 Johnson 150hp low???

I know this is a real old post, but could someone point me in the right direction to "decarb" my Johnson 150?

 

[kenmyfam]

Re: compression on my 85 Johnson 150hp low???

I know this is a real old post, but could someone point me in the right direction to "decarb" my Johnson 150?

Follow this link. You can use the "Top Secret Files" for a lot of the everyday stuff. Another tip for you. Don't be afraid to start your own thread to ask a question.

http://forums.iboats.com/showthread.php?t=302825

 

[emdsapmgr]

Re: compression on my 85 Johnson 150hp low???

At 85 lbs, the engine compression is a little low. Repeating the decarb process is a good idea. Would be nice to get it up to a more normal 95 lbs. The factory did make a low compression kit for this engine which was a factory solution to the poor gas of the 80's. Possible that this engine has that kit-which involved thicker head gaskets.

 

[kenmyfam]

Re: compression on my 85 Johnson 150hp low???

At 85 lbs, the engine compression is a little low. Repeating the decarb process is a good idea. Would be nice to get it up to a more normal 95 lbs. The factory did make a low compression kit for this engine which was a factory solution to the poor gas of the 80's. Possible that this engine has that kit-which involved thicker head gaskets.

This thread is from 2003. Someone just jumped in on it with a question 6 years later.