1998 2 stroke 50 HP HETO alarm?

[Brettoes]

Hello,
My motor has just started alarming yesterday when I was travelling along at full revs(5200), dropped it back to neutral alarm stopped, started off again and 45 seconds later alarmed again. Had been in open water so no obstruction. Tried it again at full revs and after 30 seconds alarm. Water coming from pee hole so I didn't pick up any debris so travelled back to the ramp at 3000 revs for 15 minutes and no alarm. Tried it one last time at full revs and 30 seconds later alarm.
Got home and run it with muffs on and run fine with no alarms.
Any idea's would be great, I was thinking blockage,thermostat or impeller but thats only 3 months old, so before I start pulling it apart a rough idea would be great if any one has had this issue before.also the oil tank is full and had been cleaned 3 months ago so I doubt it's that either.
Cheers
Brett

[Brettoes]

So I pulled the thermostat off and looked ok, check it opened at 50 degrees Celsius and it was fine opened well. Pulled the leg off to check the impeller and the too was fine, so took it for a run and again fine at low revs and after 30 seconds at full revs alarmed and checked the water out of the pee hole and it was warm to hot but not enough to set off the thermo switch for high temp.
Guessing it's an oil problem but it all seems to be working fine.
Any help or has anyone else had this problem, other then the alarm it starts and runs fine. Thanks

[99yam40]

You can disconnect the temperature alarm wiring at the switch when alarm is sounding to make sure that is what is causing the alarm to sound.

If it is over temp ,pull and test the switch to make sure it operates in spec

May have some blockage in cooling passages if pump , switch, and stat are working properly.