Cool 40 hp merc 1984

[RetNav]

I go fishing with a cousin that has a 40 merc that runs rough. We ran some sea foam through it and on checking the temp of the heads, both with a temp gun and putting my hand on the head right side of the plugs it is cool to the touch. (around 74 degrees after running 15 mins)Checking the tempo of the exhaust shows cool water coming out of the through hub and the pee stream. Is this normal or do I have a stuck open thermostat? If so where might it be located?

 

[Laddies]

Re: Cool 40 hp merc 1984

Thats normal there is no thermostat

 

[RetNav]

Re: Cool 40 hp merc 1984

Thanks Laddies, I appreciate the information.

 

[Laotzu]

Re: Cool 40 hp merc 1984

RetNav, when I installed a temp guage on my 50, the needle wouldn't get off the pin. I wrote an e-mail to Mercury,asking the same question you had and they answered back that the lower HP Merc's run cold. Mine don't run as cold as yours, but I have a thermostat.<br /><br />Installing the guage was not totally useless, it will still let me know if I'm overheating.<br /><br />Jerry

 

[RetNav]

Re: Cool 40 hp merc 1984

Thanks for the reply Jerry, I was concerned about the cool temp as the plugs kept fouling and I discovered the problem after talking to my cousin. He mixes at 3 oz to the gallon and then gives it a little extra to make sure it is lublicated. As he makes short trips and never empties the tank the build up of oil in the mix kept getting more and more oil.