78 115 johnson cranking compression?

[zaneh]

I recently bought a 78 115 johnson V4. 3 Cylinders have 124-125 lbs, one has only 50 (ouch). I checked the bore and piston with a light and the cylinder isn't scored and the piston looks good. Do these engines have probs with the rings sticking from carbon? Any info would be a great help! Thanks.<br /><br />Zane

 

[Bob_VT]

Re: 78 115 johnson cranking compression?

De-carb it....de-carb the heck out of it and check the compression again. Worth a try and fairly easy on your wallet.<br /><br />Bob

 

[Hooty]

Re: 78 115 johnson cranking compression?

Yo zaneh,<br />I'd give that puppy a real good de-carbonizing and see if that didn't bring the compression up.<br />Sure can't hurt. Keep us posted <br /><br />g'luck & c/6<br /><br />Hooty

 

[Franki]

Re: 78 115 johnson cranking compression?

Yeah, decarb it, soak that puppy in OMC engine tuner .. sppray it down the plug holes and let it sit for an hour or 5.. then run it for 30 minutes, then test the compression again..<br /><br />let us know how you go, I find this very interesting for some reason. <br /><br />regards<br /><br />Frank

 

[BKool68]

Re: 78 115 johnson cranking compression?

I understand the benefit of the de-carb. What about the risk of further damage to the cylinder by running for 30 minutes with a broken ring or so? Would it not be better to pull the head and side cover to really see the problem cylinder better?

 

[zaneh]

Re: 78 115 johnson cranking compression?

I was thinking the same thing as BK 68,......I planned to pull the inspection cover and head. If things look ok I'll try to decarbonize it. I've rebuilt alot of car engines and many two strokes over the years and they were all scored if they had a broken ring. This bore really looks good which kinda stumps me. It would be nice if the rings are stuck (it's nice to dream anyway) but I'm not holding my breath. If it's bad I'm going to put my tried and true 77 1150 mercury on it. Too bad, I never had a V4 Johnson and was anxious to see how it would perform in comparison to the old "Tower of Power". Thanks for the replys.