My Yamaha F90 is making oil!

[searanger]

I'm hoping for some good advice here.

I have a 2006 F90 fuel injected 4 stroke with ~315 hours.

Recently I notcied that the oil level had risen significantly.

Had a look at the thermostat, and found that it was stuck open. Changed the oil and tried to free up the thermostat.

Put about 6 hours on the motor, and when I checked, I found that the oil level had risen again.

Put a new thermostat in, put on another 4 hours, and found a slight increase in oil level again.

Oil does not look milky, and I am not able to detect gasoline smell in it.

Motor starts up immediately and runs very strong and smoothly.

Has anyone here had similar experiences? What could be the problem?

[ausnoelm]

make sure motor is coming up to operating temperature, and make sure you run it at higher RPM for a decent amount of time, low temp and low speed/short trips will cause you to "make oil"

[99yam40]

Check or replace the fuel pump

[searanger]

Turns out I probably just had put a little too much oil in after replacing thermostat and changing oil.

Did another oil change and after about 15 hours of running, the oil level is completely stable.

So most likely it was the open thermostat that caused the issue after all.