Yamaha Model C85TLRQ Overtemp Alarm

[jeh2@aol.com]

Hello,

I am having a intermittent problem that I hoped someone may be able to help me with. I keep getting an overtemp alarm when the motor is not at higher RPMs. I have replaced the Impeller, housing and associated parts. I replaced the thermostat thinking that it might be sticking. I have flushed the cooling system with vinegar, also with simple green to make sure the system had no obstructions. None of the things listed above helped. When the motor is at Higher RPMs, I have no issues, but when running at low speed, the alarm sounds. Any ideas out there?

Thanks in advance,
John

[99yam40]

does this motor have a PRV( pressure relief valve)?

If it does and if the valve is stuck open it will cause low flow and overheat at lower RPMs, but Ok at high RPM

[jeh2@aol.com]

Right below the Thermostat, there is a spring loaded plunger that seems to be functional. The spring appears to keep the plunger closed. I am assuming that this is the PRV.

[robert graham]

Right below the Thermostat, there is a spring loaded plunger that seems to be functional. The spring appears to keep the plunger closed. I am assuming that this is the PRV.

Yep, that's the PRV....did you replace that stainless steel wear plate that the impeller sits against?....