Cooling Down a Hot Engine

I've recently learned something about engine cooling on my motor glider which has application for boats as well.

When you add antifreeze solution to the cooling water on an engine, the heat transfer capability of the liquid is reduced. With a 50% anti-freeze solution, if the cooling capability of the engine is marginal, it will run as much as 25 degrees F warmer.

Get rid of the anti-freeze (not a good idea because there are chemicals in it which protect the engine) and the temperature will go down.

So what do you do if your engine is running a bit warm? Assuming you have tried all the usual cures (checking salt water flow, cleaning the heat exchanger, checking the thermostat), you can gain quite a bit of heat transfer efficiency by reducing the percentage of anti-freeze down towards 20%.

There's another trick, which works in racing cars, and which we are using in my motor glider. That is to add a small amount of a product called Water Wetter, by Red Line, to the coolant. This enhances the heat transfer ability of the coolant. We picked some up at our local Pep Boys automotive store.

If you store your boat where it is cold, make sure you've got enough anti-freeze this winter!