I got it running! '63 40hp - thermostat?

[baytonemus]

I was pretty excited tonight when I got the 1963 Big Twin 40hp (40352D) that I've been working on all summer to start and run! Lots of white smoke, but I now understand that might be pretty normal at 24:1 in a barrel.

I was afraid to run it too long but I wanted to see some water come out the back of the motor. It did start to sputter a bit after a couple of minutes.

With a cold fresh water supply running through the barrel, how long should it take for the thermostat to fully open? And once it does, how much water should I be seeing?

Thanks to everyone who has helped along the way, especially F_R!

 

[F_R]

Re: I got it running! '63 40hp - thermostat?

How long should it take??? That is impossible to answer, except to say as along as it takes to reach proper operating temperature. You need to understnad the way it works.

The water pump sends water up to and through the powerhead. Then the water is presented to the thermostat for inspection. If the 'stat says it is less than its opening temperature, the water is sent back to the pump for recirculation. Then it is sent back for another trip through the cooling system. Once the thermostat is satisfied that it is warm enough, it opens and the water is discharged and replaced with fresh cool water from the lake and the whole process starts all over again.

However, the above explanation is over simplified. Even while in the recirculation mode, some water bypasses the thermostat and is discharged and replaced with cool lake water. That is necessary in order to keep the exhaust housing cool. Also, it provides you with that visual spray so you can see that it is working.

So, the thermostat is constantly sampling the water temperature and opening and closing as necessary to maintain proper operating temperature. It is not a matter of taking x number of minutes to open, and then stay open. At idle speed it may never open, especially in cold lake water, because enough cold water is being added to the mix to replace that which was discharged through the bypass.

Summing up, there should ALWAYS be SOME water being discharged. The AMOUNT of discharge spray constantly varies according to whether the thermostat is open or closed at the moment.

If you think about it, this is exactly how all cars work. The thermostat is constantly sampling the temperature and either sending the water to the lake (radiator) or recirculating it back through the engine till it is warm enough. The only difference is cars don't have to discharge some to cool the exhaust. And you sure as hang don't want to touch the exhaust pipes either.

 

[baytonemus]

Re: I got it running! '63 40hp - thermostat?

Thanks for that very thorough explanation, F_R. Just a couple of questions for clarification...

HEven while in the recirculation mode, some water bypasses the thermostat and is discharged and replaced with cool lake water. That is necessary in order to keep the exhaust housing cool.

So some of the water is coming out the back (the exhaust relief port?), but some is also being sprayed inside the outer exhaust housing, is that correct? Is it then discharged along with the exhaust through the small holes on the bottom of that housing?

At idle speed it may never open, especially in cold lake water, because enough cold water is being added to the mix to replace that which was discharged through the bypass.

I would suspect that this is not ideal, is it? Most motors need to get up to proper operating temp in order to work well.

 

[Chris1956]

Re: I got it running! '63 40hp - thermostat?

The rear exhaust port will spit when the 'stat is open. That is not the only place that water will discharge, however, it is the only place above the waterline where it discharges. Stick a meat thermeter up the exhaust port. It should show about 140*F. If so, that is perfect.

 

[baytonemus]

Re: I got it running! '63 40hp - thermostat?

The rear exhaust port will spit when the 'stat is open. That is not the only place that water will discharge, however, it is the only place above the waterline where it discharges. Stick a meat thermeter up the exhaust port. It should show about 140*F. If so, that is perfect.

Later on, though, won't that give my roast a kind of 'gassy' taste?

Thanks!

 

[F_R]

Re: I got it running! '63 40hp - thermostat?

Quote:
"So some of the water is coming out the back (the exhaust relief port?), but some is also being sprayed inside the outer exhaust housing, is that correct? Is it then discharged along with the exhaust through the small holes on the bottom of that housing?"

That is correct, except it goes out the exhaust outlet behind the prop.

Don't be concerned about the recirculation in idle mode. It still is warming up a lot better than non-thermostat motors do.