65 PSI on all three cyl

[happyfin]

Hello .. I have a 1995 70hp Tohatsu 2 stroke Three cylinder motor. (M70B) It runs good and sounds fine, however yesterday i decided to check the compression. The results were 65 psi on all 3 cylinders. I also noticed that there was a small amount of oil on the spark plugs when I removed them.... I completed the test several times...Am I doing something wrong? Exactly 65 psi on all? can rings all go bad in exactly the same specs? Will a decarb fix this...Not sure if that has ever been done to the motor. Any help would be appreciated...Thanks

 

[ajgraz]

Re: 65 PSI on all three cyl

Was the motor hot or cold when you checked it? Did you prop the carb(s) open?

 

[Barnacle_Bill]

Re: 65 PSI on all three cyl

Check it again with a different gauge. Most auto parts stores will loan you one.

 

[JB]

Re: 65 PSI on all three cyl

Howdy, happyfin.

Welcome to iboats.

The probability that all three would go bad by the same amount at the same time. . .particularly on an engine that runs good. . .is a bit less than zero.

Take a look at the procedure listed in the Engine FAQs Forum. Either your gauge or your technique probably fall short.

 

[happyfin]

Re: 65 PSI on all three cyl

I completed the procedure exactly as the manual directed. I will try another guage..Thanks for the responses. I figured that the odds of them all going bad to the exact same degree would be high. Just wasnt sure. I started to panic. What about the oil on the spark plugs? they seem clean other than the oil. No build up or damage. I will get a different gauge and try it again in the morning. I'll let you guys know what happens. Thanks for the welcome. I have used this website many many times to fix my volvo penta. I would just find an old thread that was the same as the problem I was having. For this one however I had to join and ask myself. Thanks for the warm welcome.

 

[Sea Rider]

Re: 65 PSI on all three cyl

Tohatsu recommends to operate engine to normal operating temp, stop engine, disconnect ignition system or lanyard, remove plugs and install tester, place throttle fully open and crank engine with starter for at least 4 compression strokes, take reading for each cylinder. It's normal to find light amount of oil on plugs, it's a 2 stroke engine. If that engine has not received a good Power Tuner clean since new, it's time to do so, definitely will run smoother & better, just follow can instructions. Test with other gauge.

Happy Boating

 

[happyfin]

Re: 65 PSI on all three cyl

Thanks, I will re-check with a different gaugeand decarb this weekend. Will update

 

[JB]

Re: 65 PSI on all three cyl

Don't get hypochondria about your measured compression, happyfin. Your engine compresses the same on all three and she runs good. That is a healthy engine. Let her alone.

 

[happyfin]

Re: 65 PSI on all three cyl

Thanks JB... feeling better

 

[happyfin]

Re: 65 PSI on all three cyl

UPDATE I went and bought a new compression gauge and re-tested my motor...125 psi on all three...you guys were right...thanks for the help... HAPPY