General wisdom on thermostats for oldies…

[crosbyman]

I have a couple of motors (9.5s and 5.5 Jubile) ready to test out …………………when lake water is not so hard .

what is the general accepted wisdom on thermostats

a- run the motors and see if they get hot (fixem if they go bad)

b- open them up and test them out as a precaution (requires possible bolt breaks, new thermostats seals etc… )

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[frankr]

That’s a good topic to start a “discussion”. My personal opinion –good or bad–is those things are a lot more reliable than people give them credit for. Especially in fresh water. Salt water, well……

Even if they do fail, 99% of the time they fail open, no damage done. What you decide to do with the other 1% is your decision, I guess.

BTW, when is the last time you had a thermostat fail in your car? Same thing, but bigger.

[Steve D]

My approach is “b”

I always open it up to see what’s going on in there. Simple test in hot enough water to open them up. If it opens I keep using it. I don’t like running without at least a good used thermostat.

If it’s someone else’s motor I always check because someone may have already removed it and the motor will then run cold without it. If it costs me a seal or gasket to check it, so be it. Lot of times the seal is mangled in there anyways and needs replacing, or a lot of deposits and buildup that should be cleaned out.

• This reply was modified 5 years, 3 months ago by Steve D.

[fleetwin]

Well, there are a few factors to consider…. Are you just trying to run this engine to evaluate it, have you or are you planning to do a thorough servicing on the engine? Is it a fresh or salt water engine?
Needless to say, if this is an engine you are just going to sell, I would simply run it and evaluate the cooling/thermostat, especially if it is a salt water engine.
But, if this is an engine you are planning to service properly, or use frequently, it might be worth having a closer look. Most of these engines have only three screws retaining the thermostat, but salt water engines might require heat to loosen up the screws.
Like Frank says, thermostats are fairly reliable when used in fresh water. Salt water use plugs up passages, and corrosion hinders proper operation. I guess if I was going through all the trouble to inspect the thermostat, I would probably just replace it and its rubber seal. True, you can test the thermostats in boiling water, but sometimes they will get too hot and get ruined during the inspection/testing.
And again, like Frank says, the failure mode is usually stuck/blown open. It is rare for a thermostat to fail in the closed position, except when jammed up with salt. The one thing that should not be done is just to discard the thermostat and run the engine without it. Leaving the thermostat out creates uncontrolled cooling, and could cause hot spots/partial overheating. An engine that runs too cold will not idle properly, smoke more, and be more likely to foul plugs.

[crosbyman]

Gentlemen,

thanks for the comments. these engine are all freshwater motors and I think I will simply test them out and check them out with the IR gun

these motors are basically 50$? $60 CDN purchases to keep me busy in the winter .

I service the carbs, coils, plug wires points, impeller, gear oil etc… to get them out of their coma and sell them back out to recoup my costs with a money back warranty (till the purchaser is satisfied with is purchase …with the understanding that these are 50-60 year old motors !!!)

profit margin 0 % a couple came back for small things which I cleared up quickly (broken cord, rewind spring , cracked fuel cap on a square pump)

sold a 4, 5.5, 7.5 , qd, fd, 2x 9,5 ..all $150 CDN

Now I need to stop fixing them …for a while till I sell a couple of them ….. 2 x JW, 3×9.5 and a 5.5 Jubile …but I keep my eyes open 🙂

Joining AOMCI has priviledges 🙂

[fleetwin]

Sounds like the right approach for affordable fresh water engines for sale…

[jeff-register]

If you check a T-stat in hot water use a temp gauge to see at what temp it opens & suspend both as to not “read” the temp of the pot & of the water please. My wife hates when I bake a block, but that’s another story.

[Author]

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