compression high?

[dbradley]

Good morning! I am brand new here and tried to find an introduction page but didn't see one so please forgive me if I over looked it.

I am from Atlanta, GA and just acquired a 99' C115TLRX 2 stroke (my first Yami outboard ever).

I have not physically run the compression checks myself but the owner supposededly had them run by his mechanic before I picked boat up. According to what he gave me, the number are
Star #1-145 and #3-145, Port #2-143 and #4-143. My question is: Are the compression numbers high? I was thinking they should be down in the 115's, but never having owned a Yami I wasn't sure.

Second question: What should my oil to gas ratio be since this is not oil injected?

Thanks for the help and look forward to being on board!
Dave-Atl, GA

[rodbolt17]

numbers look good to me.
pre-mix models use 50/1 TCW3 oil.

[boscoe99]

The numbers seem on the high side to me but then most marine compression gauges are not tested yearly for accuracy. The gauge may simply be off. Gauges can live a rough life if not protected and cared for.

Consistency between cylinders is also important and yours look fine.

You can go to Yamahas website and down load an owners manual for the oil mix ratio and lots of other important information.

Owners Manuals | Yamaha Outboards

[almetelo]

What a to high compression may cause?

[boscoe99]

What a to high compression may cause?

Excessive carbon buildup can result in abnormally high compression.

Excessive compression can (not will) result in detonation. Particularly if the fuel is old, tired and degraded.

[rodbolt17]

but the odds your going to raise compression that evenly are slim to none.
would do better with the powerball.

numbers in the 140-150 range are normal for that motor.

about the same for the older 2.6 carbed V6 motors.

[almetelo]

would do better with the powerball.

What you mean?

[99yam40]

he was referring to playing the lottery, very high odds against you winning

[almetelo]

thanks 99yam40

[dbradley]

Thanks for the help guys! I knew someone knew.