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I have a 1999 250Hp. Owned since it was new. this summer it will run all day at 3000-3500RPM's. When induced above this it stops abruptly. I have carefully maintained the motor. It has 300 hours+-.
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wesh,
When you say it "stops abruply", do you mean it dies, or just starts missing real bad and the rpm drops?
Your motor could be going into rpm reduction mode due to overheat signal from the thermo sensors. This should be accompanied by the alarm going off. You throttle back and let the motor run at idle until the motor cools down and the alarm stops.
Check the alarm by unplugging the wire pair that lead to either thermo switch - there should be two, one mounted in each head assy. There are bullet connectors about four inches away from the thermo switch. Short together the two wires that lead back to the ignition control with the ignition on (do not start the motor). The alarm should sound - if not, then the alarm/circuit is bad.
The thermo switches are designed to close at around 185 degrees to signal to the ignition control that an overheat condition exists. I have seen them go bad and close as low as 130, giving a false alarm.
Get yourself a Yamaha shop manual to guide you along with the testing.
Good luck,
Ken K
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