yamaha f100 running hot

[DJ II]

I have a 2002 f100 that runs fine for a while. I can run it for an hour or so and everthing is fine. Then all of a sudden it starts running hot at idle. It never runs hot at high rpms and only does at idle or very low rpms. It does not do it all the time. Sometimes I can run it for a couple hours and everthing is fine. When the alarm goes off I cut the motor off and wait for 10-15 seconds, start it up and everything is fine. Then little while later it gets hot again. I have had the thermostat replaced, impeller replaced, poppet valves checked. The motor is peeing good at all times. When the alarm goes off the water coming out of pee hole is very hot so I know it is overheating. Any ideas?

 

[DJ II]

Re: yamaha f100 running hot

I I hooked up the muffs and noticed that if I leave it in neutral but increase the rpms very slightly that it will not overheat. I also had the powerhead removed and cleaned out water pickup tube. My mechanic said that the water pump and housing is fine but I think this may be the issue. Or could the motor be idling too low and could I just increase the rpms at idle to correct the problem.

 

[rodbolt]

Re: yamaha f100 running hot

myself I would double check the water pump,double check the pressure control valve before looking in the midsection.