Change 1984 70HP Thermostat

[JohnWI]

What parts are all needed to to the job? I'm surprised there's no "kit" available with what's needed.

I'd assume the cover would be OK, but what about gaskets, spring, etc.?

I can't be 100% sure as my temp gun was used while rocking in the chop while pointed at the cyl heads but seemed to only go in the 80-90 degree range on the three heads. The tell tale was only luke warm. Would the TT normally be the same temp as the engine or does it not get as hot?

 

[oldcatamount]

Re: Change 1984 70HP Thermostat

All you shoud need is the T-stat and the cover gasket. The T-stat controls the temp of the motor which should be alot higher than 80 or 90 degrees (probably nearer 120-140+ degrees). The pee stream will feel cooler because it's not traveling through the entire water jacket.

 

[WernerF]

Re: Change 1984 70HP Thermostat

Not properly closing is typical for a thermostat >20 years old.
You may replace the vernatherm alone or the thermostat assembly which also contains the plastic housing. I prefer the latter.

 

[JohnWI]

Re: Change 1984 70HP Thermostat

So do I understand the function of the thermostat and relief valves as follows?:

Pressure valves do nothing (closed) at idle.
Thermostat opens up during idle as needed.
The pressure valves open up and more as the RPMs increase thus becoming like an automatic thermostat (more RPMs [making more heat]=more water passage=more cooling)

Also, the new thermostat is shorter than the original and the new gasket was shaped the same on the outer shell but there was an extra, internal part of gasket ...kind of like it would be used for a different part that had another mating surface. The part number was the right one. I debated cutting it out to match the original shape, but felt it didn't hinder the pieces fitting the right way.

While using my temp gun I was seeing only about 115 at idle and 130 on operating conditions. Sure, it's better than 80-90, but does this seem good? The manual seems to state the temps to be mid 120s on the low side to a max of low 160's on the high side.