Temperature Question 1982 50 HP Merc

[joezek]

I've got a 1982 Merc 50HP on a Grumman 15ft boat, that's been in the family for 28 years. It's never been overhauled, and guestimated it has around 1,000 hours on it. It's always been flushed with fresh water after each use, along with the fuel disconnected to let the carbs run themselves out.

I just was given this boat and changed the water pump impeller as soon as I got it. I've noticed though that the **** stream gets so hot that it's steaming the entire way from the engine to the river/water. You can barely hold you hand in it because it's so hot. I thought the water would be around 150 but it feels much hotter.

I don't think it has a thermostat, and the stream is pretty strong so I don't know if there's anything wrong with it or not. I imagine that the water paths inside this engine are pretty small and possibly corroding or have buildup. Is there a flush that will strip/dissolve all loose build up in one shot? Are there any home recipes for making something that will dissolve the buildup, or just use a good radiator flush?

 

[joezek]

Re: Temperature Question 1982 50 HP Merc

I hate to reply to my own post but I just thought of one other piece of information. There's been a noticeable drop in maximum rpm's lately, around 500 rpm. It still runs smooth, just lacking full power. Could it be possible for a head gasket to be leaking and causing high temps, and low power?

 

[joezek]

Re: Temperature Question 1982 50 HP Merc

Any thoughts anyone? Is there a way to tell if it's hotter than it should be? Is there a standard way of checking for a blown head gasket on a 2 stroke?

 

[Sunfish12]

Re: Temperature Question 1982 50 HP Merc

Rpm's drop the hotter you get the engine. The water shouldn't be hot. Do a compression test. A bad exhaust gasket can cause steam.

 

[joezek]

Re: Temperature Question 1982 50 HP Merc

The compressions were all between 145-150 cold. I did it with and without spark plugs in the other cylinders and the results were the same.