470 Overheat

[dan4836]

After looking closely at my thermostat and housing, I found the thermostat installed does not close off the circuit (engine side). I have the older style manifolds and the bottom part of the thermostat is smaller than the hole that allows the coolant to flow back through the engine.

In other words, when the thermostat is closed, no water can go to the heat exchanger. when the thermostat opens, on top the coolant can flow from the bottom and through the thermostat to complete the circuit to the heat exchanger. Also, when the thermostat opens, it should close off the circuit that goes back through the engine.

- The thermostat foot is too small and does not make it to the bottom to close of the hole.

My research shows that only two thermostats are made for the 470. One for my style manifold and the other for the aluminum manifold set up.

Any suggestions?

[aussie]

Take. The thermostat out and try it. Even with the thermostat not being rite once it opens it shouldn't overheat

[dan4836]

If I take out the thermostat, the coolant will go where it wants. Some will go to the exchanger and some will go back through the engine.

[macojoe]

Make sure the T stats are in the right way! I have seen people put some in backwards and they can't work right! Can't do it with all but some you can, worth a try.
Are you sure the T stas are opening?? take out and put in boiling water see if they open and close when they get cool? Might need new ones?
Motor water pump, mine had the impeller rot off it and could not move the water, someone had put a auto water pump on it.

[dan4836]

I had a marine mechanic come over to take a look and this is what we found.

The thermostat that is installed does not look correct and I was to purchase another thermostat for the 470 that looks like it will do its job. The new thermostat part numbers match up with the newer, aluminum manifolds.

From what we see, the part number of the thermostat installed is the correct part number but it does not look like it will redirect the coolant to the heat exchanger.

The mechanic said my setup is unusual because the thermostat does more than one function. It lets water go to the heat exchanger and closes the hole the goes back to the engine.

I will see on Saturday during a test ride...

[dan4836]

Found my problem! After replacing just about everything, I found my thermostat is incorrect.

I researched this for weeks and found the thermostat my engine calls for matches to a Mercruiser part number that is incorrect. I put the thermostat for the newer, aluminum type manifold in my older cast iron type (first generation 470) and it worked perfect. 170 degrees at 4000 RPMs for ten minutes.

I wonder how many other people are using the incorrect thermostat in their 470 based on Mercruiser's numbers.

Now I can post about other restoration projects and maybe show some fish pictures this year!

[aussie]

Glad you found the problem will have to make sure I use the correct one Hey spares no input from you on this one