compression is mine ok ??

[quebec#1]

I took my compression this weekend on my 1986 110hp johnson and got 108/100/115/115. on the four cylinders. Cold reading..Some post seem to say anything over 100psi is great others have said 130+ im sure when it was new this motor put out 120psi ???

 

[R.Johnson]

Re: compression is mine ok ??

Those readings are correct, though I would pull the cylinder head to look at that #100 reading.

 

[JB]

Re: compression is mine ok ??

I agree with RJohnson, Gary. <br /><br />Absolute psi readings vary a lot from one guage and one technique to another, so the important number is the spread. 15% is about a maximum allowable spread, and you are there.<br /><br />Try decarbing the engine and check compression again before you start pulling heads.<br /><br />Good luck.

 

[Solittle]

Re: compression is mine ok ??

I have a pair of 1987s and mine are in the same ballpark. No problem.

 

[quebec#1]

Re: compression is mine ok ??

Thats great to know ! The engine has served me very well over the years, It must have at least 300 hours if not more on it. I just put gas in and go and fog it well at the end of the season and change the plugs every so often. I think this guage is almost right on, my old guage was off at least by 10psi when i took the readings on my snowmobile but with the new one it was right on with the same readings from the guage that my buddy has at his shop.

 

[quebec#1]

Re: compression is mine ok ??

JB, I never ever decarbed the engine i cant get that goop that everyone uses but the omc spray is around. Question everyone says to pull out the little red pick on top of the carb, How do you pull it out ? Do you twist it out? or is their some type addition nossel that goes over it ? Thanks for your help!....

 

[R.Johnson]

Re: compression is mine ok ??

Spray the engine tuner directly into the carb throat with the airbox cover off. Don't try to pull that red stem out of the primer, It is held with a detent.

 

[reeldutch]

Re: compression is mine ok ??

15 psi is borderline and reason to check things out.<br />i would spray some fogging oil in the 100 psi cylinder. and than repeat the compressiontest.<br />if your rings are sticking the fogging oil will raise the compression to close the leak. then a decarb will be helpfull.<br />if the compression test with fogging oil is still 100 psi the rings might be broken and a Decarb will not help. But don't get me wrong 100 psi is still acceptable only why is there the difference?<br />lean running carb??? are the 100 and 108 psi the top ore bottem cylinders.<br />if so i guarantee you are running lean.<br />rebuild your carbs to be safe!!!!!!!!!<br /><br />good luck