50hp Cooling Advice Needed

[MNSubbie]

I bought a 1980 50 hp 4 cyl Merc that had very little use. It is so clean under the cowl, you could eat off it, and it really does look and run like a brand new motor.

But I am concerned about the cooling. I cleaned out the water discharge tube----was plugged up from insects---and now that pisses out an abnormally strong stream of water. But that stream is VERY hot. I cannot hold my fingers in it. My other outboards, including the 1990 40hp I currently have only had a "warm" stream.

I am going to change the impeller, just on general principles (if its original, it is 36 yrs old). But should I be looking for something else? The telltale stream is way stronger than what I consider normal, and its way hotter than normal. Could I have some blockage somewhere (more insects??) Don't think this engine has a Thermostat, but maybe it has a poppet valve somewhere that is stuck??

Would like to fix this before I ruin a spotless older motor. What should I be looking for? Any and all advice would be much appreciated

 

[Texasmark]

Sounds like the "Classic 50" which is a later version of the original 4 cyl 40 hp engine of the 40's. No stat on that engine. On your impeller, expect to have pieces of rubber all over the water passages if your impeller blades are missing parts which, at that age, should be. With no stat and idling, water should be barely noticeably warm on a spring morning.

 

[GA_Boater]

Are you running on muffs, in a barrel or on the lake?

On muffs my 50, an earlier version of yours, has a very warm, almost hot tell-tale. On the lake it's barely warm.

 

[MNSubbie]

Just a quick update on my Cooling situation---------I fixed it.

Put in a new Impeller. Expected the old one to have missing pieces like Texasmark suggested, but it didn't. Old one was just brittle and not flexible like the new one. Looked around while I had it opened up and found nothing out of the ordinary. So I simply replaced the impeller.

And now it runs much cooler. Before, I measured the tell-tale water using a meat thermometer (its all I had at the time) and the temp read about 135 degrees. With the new impeller, it doesn't even make the dial move on the thermometer. I can hold my hand in the water stream, and its just warm. Nice !!!

Hope my story helps someone else. Thanks all for the views and replies