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RJQN
07-10-2006, 11:35 AM
Help
After about 15 minutes at 4500 rpm the overheat alarm on my 1989 200ETXF goes off. If the motor is shut off for 5 minutes or so it will start and run again and the alarm wont go off again if rpm is kept at 3500 or lower but at this point it's rpm gets erratic. If running at say 3500 rpm the rpm may shoot up to 4000 or better. The carbs were rebuilt last year and the powerheads were just rebuilt. The overheat alarm problem was there prior to rebuilding.
The powerheads were rebuilt because I thought there might be a problem with clogged water passages plus compression was down to about 60psi. I was thinking maybe there was a problem with the engine leaning out at high rpm causing too hot a fuel burn.
Can anyone help
Thanks

rs657
08-02-2006, 10:17 PM
This happened on both of my boats with 1989 Yamaha 200 and 225. If your thermostats are good then check the water pressure relief valve on the back of the power head just below the coils. You will find a hose about 1/2 inch in diameter attached to it. Remove the two screws. A spring and plug will be underneath. Take some 80 grit sandpaper and hand sand the ridges on the plug that goes into the rubber grommet. This grommet gets hard after a while and the valve will not seat completely. Do not remove the grommet. It is not as easy to put back in as you think. A light coat of grease on the grommet will help too.