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Water light not working

Frank Langer

1984 Ericson 30+, Nanaimo, BC
>>add a water temp gauge.

I look at that gauge every 10 minutes while the engine is running, and I'm not the only one. It's a habit, especially when running anywhere near Wide Open Throttle. The relative readings over time let you know the rate at which the cooling system is gumming up from scale, hoses and the passage of time.. The formerly expected 180F becomes 185, then occasionally higher, then eventually pushes 200F. More a message than a warning.

It is a comfort to monitor the running temperature. A warning light is OK, but not a comfort.
Sometimes an owner will run without at thermostat if the existing one fails in a closed position. Running without a thermostat makes it harder for the engine to operate at its normal temp, but otherwise I don't think it causes any other problem or damage.
The mating surface in your pic looks ok far as I can tell, as long as any rough spots are removed. I only use the gasket, no sealant. If it doesn't seal properly, ie. it leaks, then a gasket sealant may help, but I would try without first. Tighten the bolts, but not so much as to risk breaking them off, which creates a whole new set of problems.
In not a mechanic, so just going from my experience.

Kenneth K

Sustaining Member
Blogs Author
Like Frank said, +

......not had a thermostat? And if so what does that mean for me?

It depends on how the PO used the engine. Once the engine is warmed up, the thermostat isn't doing anything, so if he was motoring for long periods of time, there should be little adverse effect on the engine. If he was charging the batteries at idle for long periods, however, the engine might have been running too cool for long periods and building up carbon on the valves, etc. Probably wouldn't hurt to do a nice, long motor, say, 2+ hours at 80% of max rpm and at full operating temperature to "blow out" the system.

Do the pics reflect a good enough cleaning of mating surfaces? or put differently, how spotless does it have to be? I'm afraid to go at it too hard and end up scoring the area. I worked at it with a new razor blade.
My last step is usually to scrub both surfaces with a Scotch-bright pad to smooth/shine them up a bit, but ONLY if you can do it without getting the shavings/cleaning debris into the engine and antifreeze.


Member III
One last question on this mini project. My 2qm15 manual (1980) doesn't say anything about the orientation of the thermostat when placed in the housing. But I came across a comment on a youtube about lining a hole on the top of the t-stat with the housing bolts, and then in an old yanmar 1gm manual I found on line i read "Install the thermostat in the housing or cylinder head with its thermostatic element facing the engine." Huh? All this to ask, does it matter how I orient the t-stat in the housing? Thanks.

Kenneth K

Sustaining Member
Blogs Author
Here's a pic of the original thermostat in my M25. I cant imagine it would matter in the slightest how the thermostat is rotated once seated. Just don't put it in upside-down.


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