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Thermostat question.

B

Balder

Contributing Member
1997 Johnson 115.
The thermostat in the outbord motor not looks like the car thermostate so i have a some questions.
Can i put the thermostat in hot water and check if they are in order ?
Do the spring only hold the thermostat in position or do the spring something more...like react to the temprature and change the positon of the thermostat ?
I am a lityle confused how this work:confused:
 
Yes, check it with hot water.

Chemicals sealed within the thermostat react to heat, causing it to open (expanding to heat).

The spring pressing against the chemical chamber as the chemical cools, when the engine is shut down, causes the thermostat to start closing.

Don't over-think the components... it'll drive you nuts. They either work or they don't.
 
Thank you for your answer.
So if i will by new thermostats i dont need to buy a kit with spring....the spring is ok if they are in one part.
Then i will put all 4 thermostats in hot water and see if they open at the same time and check that they open at about 140farenhait.
Am i correct ?
 
Balder said:
If i will by new thermostats i don't need to buy a kit with spring....the spring is okay if they are in one part.

I will put all 4 thermostats in hot water and see if they open at the same time and check that they open at about 140 degrees Am i correct ?
Click to expand...

I have never had a problem with the springs (since 1960 to 1991), having retired in 1991. See no reason why you should encounter a spring problem.

Thermostats, relying on memory open at around 143 degrees so you;'re in the ballpark. Actual degree is normally imprinted on the thermostat.
 
Balder, those thermostats only open about 3 centimeters,so break out the magnifying glass if your eyes are as bad as mine
 
Press on the spring and the valve will open and stick the string in the valve. One at a time hold the thermostat in a small pan of water and hold a meat thermometer right next to it. The thermostat should fall of the string about 140 degrees. The bulb on the thermostat is full of wax and a piston as the wax expands it pushes on the piston to open the valve.
 
The separate spring above the thermostat is a pressure relief valve. Above a certain water pressure, the whole (closed) thermostat will lift against the spring and allow water to flow even though the 'stat is closed.
 
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