No compression gain after engine tuner

[chilifriedpork]

'75 Johnson 15 with 45 pnds. compression in both cylinders.<br /><br />Let engine tuner sit for 6 hours.<br />It smoked a lot(smelled kinda weird, like minerals) and got the water in my garbage can that I run it all white and greasy.(i'm afraid to dump it now!) Let the engine run for 15 min, no compression gain. <br /><br />It starts real easy, and idles descently. It sometimes cuts out (lean idle mixture?)<br /><br />I'm going to take it out on a fishing trip July 22nd.<br /><br />Would I have enough time for a re-build? (Parts including, rings, possibly thermostat, head gasket and a few others)<br /><br />What are the gaskets that MUST be replaced? I have liquid gasket also.<br /><br />Thanks a bunch!

 

[wayne h]

Re: No compression gain after engine tuner

i would spray her up again and let her soak over night then take it to a lake or somthing like that and really run her hard after that install new plugs and see. as for the rebuilf i dont think you will have time if the block needs machining thats a week alone at the machine shop. also you never have all the parts you need hahaha. i would try to run her out and see what happends if she starts and runs well whats the trouble ? are you just worryed about low compression ?

 

[Walker]

Re: No compression gain after engine tuner

If it starts real easy the first thing I'd do is check the compression again with a different guage.

 

[ledgefinder]

Re: No compression gain after engine tuner

Both are 45? - maybe leaky head gasket?

 

[roscoe]

Re: No compression gain after engine tuner

I'm with Walker. If it starts easily, then compression may not be as low as you think. You may be getting a faulty reading for some reason, or the guage may be sticking or faulty.

 

[SeaMasterZ@aol.com]

Re: No compression gain after engine tuner

good call ledgefinder, busted between the cylinders

 

[chilifriedpork]

Re: No compression gain after engine tuner

I shouldn't say anything until I do a run with the motor on the boat. Then I will see if the problem is bad.<br /><br />True, the gauge could be sticking. The repair shop said it had 80 psi last summer, and it wasn't used very much at all since then.<br /><br />If reading are accurate at 45psi, then I am worried because so many things depend on good comp. <br />Even with re-building motorcycles, parts are always on back order etc. That'd be a real shame if I was missing the piston rings and had planned for a fishing trip in a few days! LOL. <br /><br />I'll leave it for now.<br />Thanks for the help.