Causes of low compression, top end rebuild.

[Kenrussell3]

Briefly, 1997 Speedster with twin Rotax 717. My first boat, purchased last fall. Seemed to be running fine. Oil light came on. Left engine running fine. Right engine died, sputtered trying to restart, and died without being able to restart since. Used the right engine to return to the boat ramp. Right engine still will not start. Checked compression. Right engine: seems to start and run fine with 80 psi at both cylinders. Left engine: will not start with 70 psi in front and 20 psi in rear. What is the usual cause of low compression? What do I look for now? Should I do the top end for both engines?

 

[Mraw]

I would get a new compression gauge and check again

 

[Kenrussell3]

You are absolutely right. I had a small engine mobile repair mechanic come over and test with his old tried and true compression gauge. Three of the four cylinders were over 125 psi. The forth cylinder was at 35 psi. He is coming back Monday to rebuild the top end of the right engine.

 

[Kenrussell3]

Thanks for the response. My gauge is brand new, and it was the first time I used it. I will have to return it.

 

[Kenrussell3]

My brain is not functioning left to right this morning. The mechanic is coming to rebuild the left engine.