TN 27 overheating

[63lstrition]

I have a TN 27 that I am working on, and it seems to be running good with the exception of cooling. It seems that the exhaust manifold is not getting cooled because it is almost instantly too hot to touch. It seems to have a good telltale, and I did have the bottom off earlier and checked the impeller and everything seemed good.

Here is a video of it running – https://youtu.be/ZEJR4msiv0A

You can see me splashing water on the manifold and it cooking off. I am assuming that something is blocking the water to the exhaust side, but could use a little guidance. Do I have to take it apart, or will a blast of compressed air work? It is relatively simple to take off the exhaust manifold to blow that out too?

Looking for some guidance

[frankr]

Does water squirt out the tell-tale hole in the copper tube elbow?

[63lstrition]

Yes. You can see that in the video, but I should have zoomed in a little more.

[frankr]

Put some more water in that bucket and try it again.

[63lstrition]

it was in a 40 gallon garbage can, but the way the motor was sitting it was a little high in the water column. I will try to lover it and add more water. Problem with that one is that neutral doesnt work and it will spit water out.

[ERROL STILLINGS]

I have just had a heating problem with a TN28 and had two problems. The rubber grommet at the top of the impeller housing was broken – AND – the
head gasket was beginning to go.

[63lstrition]

I will take a look at the gasket. It is getting hot almost immediately on the exhaust manifold – I splash water on it and it is cooking off. The heat then transfers to the jugs.

What are the symptoms of the head gasket going? Are you suggesting that the gasket might be impeding the water flow to the exhaust manifold because it is breaking down?

[ERROL STILLINGS]

The head gasket will impede water flow period. There is no flow from there. The piston, while losing power, will prevent water flow.

[Mumbles]

If a head gasket is leaking, hot combustion gases can get into the cooling system displacing the cooling water. The impeller doesn’t have enough pressure to combat the gases so the motor overheats.

[63lstrition]

Would it be good preventive maintenance to just replace the head gasket? Are they hard to get? I don’t think Marineengine has anything listed for anything earlier than ’56. They are usually my go to to start the search.

Mumbles – you mentioned in my post on the AD-12 that some motors did not have cooling to the exhaust cover. Is that the case with the TN-27? Would the TN-28 have cooling to the exhaust cover?

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