thermostat problems?

[mches106]

I need help with a 1978 Mariner 28HP thermostat.
The motor runs a little rough at low idle and the tell tale stream is cold even after 15 min. I pulled the thermostat and inspected, but I really don't know what it should look like. The selco manual dosen't mention this small part.
The little brass plug on top is up in what appears to be in the open postion and won't depress down. should it?
Also, is there a common replacement for this other than a recycled part?

 

[deejaycee_2000]

Re: thermostat problems?

the thermostat should be closed when cold, and then open up when getting hot, yes you can get a replacement, to test the thermostat, put in in a cup of hot water to see if it opens up and then put it in cold water to see if it closes .....

 

[mches106]

Re: thermostat problems?

Thanks,
I will give a try today.

 

[Texasmark]

Re: thermostat problems?

You need to check the routing of your pee line. It may come directly from the exhaust manifold and be in another circuit from the stat. If you have pee within 1 minute of cranking, it's on a different circuit and the water will not get hot (normally).

You may have an overtemp buzzer that tells you if the stat fails to open, but on that old an engine and that hp, maybe not.

The stat has a pellet on the bottom and stamped on it is the opening temp in degrees F. Like Dee said, put it in a slowly heating pan of water on the stove and put a candy thermometer in the water and watch the valve. Around the temp stamped on it the valve will start to pull back and as it gets hotter it will pull back more till fully opened.

Mark