Thermostat questing

[Peterpd99]

Hello Y'all,
My motor- 1961 evinrude 5.5
After removal, I'd cleaned it CLR and it looks brand new. The thermostat (p/n 5005440) doesn't open when immersed in boiling hot water.
I know its just metal expansion as the only moving part and what causes it to malfunction? Is there a way to revive it and make it work again or just toss it out? Not that I'm thrifty, just that I'm curious.
Thanks.

 

[Vic.S]

Surely it has a wax capsule ... the copper coloured bit in the picture, When the wax melts it expands and pushes the thermostat open. It should just start to open at 143F

It is the same part as the one in my 6 hp Yachtwin. That stuck open but descaling it and gently exercising it by hand restored it to normal operation .

If yours does not open in boiling water it has had it ! Toss it out and replace it with a new one

Sierra 18-3543 is the equivalent Sierra part number and a few $ cheaper ( still silly money though)

 

[Peterpd99]

Thanks Vic.
good explanation and info.

cheers.

 

[oldboat1]

If you want to test it a bit more, grasp the flange with a pliers, kitchen tongs, or similar, and hit the sensor at the bottom with a torch or lighter flame. If the spring moves, it's probably OK. To fine tune the test, you need to immerse it with the tongs in various temps (believe it should be fully open at 160F if a 143 degree t.stat) -- begin opening at 143, like Vic says -- reasonably close, anyway.