250hp OX66 - thermostat stuck open?

[hyd-n-seek]

Hi,

Yesterday, I noticed water sputtering out of the exhaust manifold on my 2001 250hp OX66 right after I started the engine. It seemed to stop after I had run the boat for a short while.

I'm guessing that one of the thermostats is stuck open, allowing water into the jacket before the engine heats up Does this sound right? If so,

-- what would I be looking for (debris, corrosion, etc.) as the cause of the problem?
-- Can I get at the thermostats w/o removing the flywheel cover?
-- Is it a mandatory gasket replacement if I remove them? The reason I ask is that my closest Yamaha dealer isn't all that close.
-- Do I also have to disassemble the pressure control valve assembly?

Thanks in advance for your help.

[Hamfisted]

Yes, those are good assumptions. You should inspect both the thermostats, and the pressure relief valve for debris. I would replace your current pressure relief valve with the newly redesigned PRV with the mushroom head (p/n 60H-12416-00-00 ). This new design helps prevent debris from getting stuck in there anyway and eliminating future problems. You can order the gaskets and new PRV from the guys here at Boats.net and have it mailed to your door. Along with the PRV get a new grommet seal and the gasket. The whole thing will run about $10 and you'll be much better off in the future. How old is the waterpump? If it's more than 5 years old you might as well change it too. What year is the motor?


Mike........ Miami, FL

[hyd-n-seek]

Thanks, Mike. The engine is a 2001 but I don't think it saw water until 2002, and its only got 130 hours on it total. Do you still think changing the water pump is a good idea?