99 Yamaha F100 problems-help

[mel_schutte]

Motor is newly rebuilt. starts fine but after it warms up and I increase RPMs to around 1500 and about five minutes later warning buzzer sounds and I am assuming in is for oil because water stream is great. I have a yamaha digital tach it does not light up but when I turn the key on it has a small line that flashes on and off. Water temp gauge line stops flashing a few seconds after turning the key on but the oil gauge does not. Oil level is good. RPM reduction does occur.It is fine as long as i am idling, no buzzer even after prolonged idling. Any feedback would be appreciated. One more thing, as soon as a turn off motor after buzzer I can start it right back up and about 5 minutes later it does it all over again.

[boats.net]

Thats usually a indication of overheating. If you didn't put a new water pump in it when you rebuilt engine you should. Check thermostats, pressure control valve. When you first turn ignition key on the tach should do a self test, the overheat and low oil pressure warning will flash.