Head Temp

[Kickass]

1998 yammy 115 Saltwater Series TLRW
I've already replaced most of the parts,,,IE,
temp sensors
thermostats
impellor
water pump and housing
serviced lower unit
poppit valve
I had 1 of the head covers removed and was told it was clean so no need to check the other, however I suspect this is the problem. So I want to find out if one head is hotter than the other when the overheat alarm goes off.
I am going to water test the motor, and check with a temp sensor gun, to measure the temp of the heads AFTER the alarm goes off, where should I point it, or touch it to?
AND what is the "normal" temp range, and what is considered overheating temp?

Thanks guys!
Charles

 

[yamamarinetech40]

Re: Head Temp

Well, it couldn't possibly be simpler...put your fingers on the TOP of the head, if you can hold your fingers there for three seconds...not too hot. Why wait till alarm goes off to check? See if heads FEEL about the same...hopefully your senses are more dependable than a temp guns??? Most things should be checked in water, but this is one you can do on hose first....as far as heads being CLOSE to same temp....

 

[rodbolt]

Re: Head Temp

the heads should stay less than about 155-160*, the temp switches,no sensors,should close about 185*.
first are you sure its an overheat alarm and not an oil alarm?
both use the same horn and are seperated by the visual indicate on the digital tach.
unless you have a visual indicate there is no way to differentiate oil from overheat by the operator at the helm.
in saltwater areas we periodically have to remove the cylinder head and clean the salt scale from the head pasages as the scale builds up and the temp switch is located on a blind passage.