Thermostat and operating temp question

[gener8s]

Hi all.
My 2004, Mercruiser 3.0l engine, serial # 0W00014 has always ran around 175 degrees. Even after the last impeller change in 2010. It runs great except for the classic "3.0l run-on". This season I ran only ethanol free 91 octane fuel and it did seem to help, but it didn't completely cure the problem. There are 2 thermostats that are available for my engine, the 160 that is currently in it, and a 142. Do you think the 142 would help my problem by lowering my operating temp? I am changing the impeller this year as well.
Thanks for your input,
Dave

 

[cr2k]

Re: Thermostat and operating temp question

Yes and what RPMs is your idle set at? If you get the idle down around 500-600 it should not diesel. Don't know how you run your engine but if you troll or run low RPMs a lot you may need to de-carbon as a carbon build up will also contribute to a run-on condition.

 

[gener8s]

Re: Thermostat and operating temp question

Thanks! I never really thought about the carbon issue but your right. I'm winterizing the boat =( this weekend so a can of combustion chamber cleaner wouldn't hurt anyways. I have found that if I lower my idle below 700 rpm, it's a little too rough for my liking.