Tohatsu 9.8 compression

[JET4]

I have a 2010 Tohatsu MFS9.8A3EPTS outboard. The factory service manual says the compression should be 128 psi. The dealer checked and the compression was 95 psi on both cyllinders. Is that to low? He called the factory and they said that was good. I think it's to low, is it ?

 

[pvanv]

Re: Tohatsu 9.8 compression

95 sounds a wee bit low. Is the motor broken in yet? If the rings haven't fully seated, that may be the reason for the readings. Also, some gauges read differently than others.

 

[JET4]

Re: Tohatsu 9.8 compression

The motor is broken in . Have about 20 -25 hrs. on motor. When I first got the motor it would push the boat 15 mph, now the best I can get is 10.8 mph with handheld gps

 

[TOHATSU GURU]

Re: Tohatsu 9.8 compression

The actual reading is not given much weight because of the huge variance in readings from different gauges. Even is all that is looked for...If your concern is that the boat is not as fast as it once was I would go over the boat to eliminate it as the problem and then take the engine into a different dealer and ask them to tank test it for 15 minutes.

 

[JET4]

Re: Tohatsu 9.8 compression

Thank you for your advice.

 

[pvanv]

Re: Tohatsu 9.8 compression

The actual reading is not given much weight because of the huge variance in readings from different gauges. Even is all that is looked for...If your concern is that the boat is not as fast as it once was I would go over the boat to eliminate it as the problem and then take the engine into a different dealer and ask them to tank test it for 15 minutes.

Absolutely.