What temp should a head be

[mfo]

I have a 91 150 proV that had the overheat alarm go off while idling around at very low rpm 500 rpm for 5 min or so , I replaced the waterpump and took the boat out a few times and all seemed well but last week the alarm went off again while doing the same thing idling for awhile So I changed out the t-stats and I will change out the prv, but in case it does it again I bought a infra red temp gun to shoot the head.My question is what is considered a normal temp I want to eliminate a faulty sending unit




thnx
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[rodbolt]

Re: What temp should a head be

less than about 165*F.
fresh or salt water use? and brackish IS saltwater use.

 

[mfo]

Re: What temp should a head be

the 165 is that with a temp gun? I took it out today idled 600-700 rpm quite a bit and pulled it out of the water and popped off the cowl shot the heads within 4 min of shutting it off with an infrared temp gun, had consistently 138 on the right side and 128 on the left standing behind the boat. Is that high and why the diff between sides? BTW fresh water use




thnx
mark

 

[99yam40]

Re: What temp should a head be

Best to read temp while motor is running , not after has been shut down to get the proper temp the motor is running