Evinrude 15, 1980 water circulation

[Mikko]

I have changed the head gasket, t-stat (at the bottom) and cover gasket in the motor in the 3rd picture. Since then I have not used it much. I used it in the tank only 10 minutes or so and the highest temp was only 40 deg C. I do not know the routing of the water passages, but I thought water should not come out from the exhaust relief right after the start, but after the t-stat has opened? Anyway, there are a bit different exhaust systems/pipes in these two motors (1980 and 1982). In this newer one there is a short water outlet pipe which reaches lower than the exhaust relief hole. Therefore, I think less water is coming out from this hole after the t-stat has opened.

As seen in the middle picture I used the laser temp measuring device and it was easy to find the hottest point in the power head. It was in the middle of the t-stat cover, after the t-stat which makes sense as t-stat has not opened yet, I guess. Same temp was found in the left side (from behind) of cylinder, but right side and top of cylinder was much cooler.

 

[oldboat1]

That 40 degree reading sounds fine. My '83 runs 120F or so at the head, maybe a little cooler, but will come up some with longer operation. Depends on lake temp too for initial temp and warm up time. It exhausts some water from the port after starting, but can tell when the t.stat opens with the increase in flow. Tell tale is stronger or weaker, depending on spiders and such around the stern (trolling motor on a boat in a slip). Laser gun is fun to use. Time to go run 'em.

 

[Mikko]

I am still wondering why there is so much water coming out from the exhaust relief hole (3rd picture above) right after the start. I have not pulled this power head but as far as I understand there should not be any connection between water inlet and outlet at this level as the inlet copper tube connects to power and continues to the pee hole and further to the head. Water must go through the t-stat before entering the exhaust relief holes? In this motor there are two of those exhaust holes and as seen in picture 1, only one in another motor. Still I think the water passages are same in both motors? When so much water is coming out right after the start, what is the water route then?

 

[oldboat1]

t.stat bypass in the t.stat housing.

 

[Mikko]

It is one year gone since last posting on this topic. I have tested the Evinrudes in this summer and it seems that they are both ok, I have used them quite a lot without any problems. My question now is if it is ok that after long use with full throttle on the lake the hottiest temp measured was almost 185 F (85 C degrees)? This was couple of minutes after shut down of the motor when there was no cooling any more. I think it may be normal as the head is hot and not cooled any longer. First time when I measured the temp after use, it was only 150, but at that time I kept the motor idling and water circulating.

 

[oldboat1]

Hi again, Mikko. I think you might have answered your question. If you let it idle a bit before shutting down, you get continued cooling circulation while naturally running cooler at lower rpms. (Think that's somewhere in the instructions for my old inboard, and seems like a good habit.)