1985 Mercury 115 Inline 6 experience?

[Aquasport76]

Hello all. Last year I purchased a 1976 AquaSport 196 w/ a 1985 Mercury 115 Tower of Power. I love the engine and the power it puts out. I have not had any issues with the engine but I did notice after running the engine the tell tale water gets rather hot, hot enough to the point where I can only put my hand under for a few seconds. Is this normal for these engines? Do these engines have a thermostat? I changed the impeller but still no change. The tell tale stream is strong. I am unsure if this year engine is equipped with an overheat alarm therefor I am unsure if the engine is overheating. Any help would be greatly appreciated.

 

[jimmbo]

No thermostat, or overheat alarm. On the 1985 engines the telltale tap is on the top of the block, so it is well heated

 

[Aquasport76]

Thanks for the response jimmbo. Would it be safe to say the block is getting an adequate amount of water judging from the telltale stream?

 

[jimmbo]

Is the stream steady, with no spurts of air? Unless there is a blockage preventing water from exiting the engine normally, you should be ok cooling wise

With the engine running on a set of Muffs, there should a fair bit of water coming out of the prop, and various other drains, If there is little water besides the tell tale then there might be problems.

The cooling system of those engines is very simple, reliable. The biggest issue is worn/broken water pump impellers, and warped water jacket covers, resulting in water leaking around the spark plugs, usually the top ones

 

[Aquasport76]

The stream only generates spurts of air when I am running it on muffs. When I’m running on the water it is a steady stream. I will have to check the water discharge out of the prop and other drains this weekend. Thanks again jimmbo

 

[Texasmark]

Thanks for the response jimmbo. Would it be safe to say the block is getting an adequate amount of water judging from the telltale stream?

The domestic hot water heater normal setting is 140F. I had an '88 and as jimmbo stated, no stat and no Ot alarm. My '02 90 had both and the stat opening temp was stamped on the pellet at 143F which will have a few degrees tolerance and will have a range of hotter temps as it moves to fully open. So there are a couple of benchmark numbers.

If you haven't changed the lower unit oil and replaced the impeller or the water pump or other pump parts if required in awhile, now would be a good to do it...while you are thinking about it.