1976 SeaRay with Mercruiser 233 (ford 351) is overheating :(

Hello Everyone!

We have a 1976 22ft Searay with a Mercruiser 233 (Ford 351 v8) that is over heating.

We're bypassing outdrive and plugging in hose directly to water inlet. Thermostat housing replaced, water pump replaced, and manifolds and exhaust elbows have been cleaned out.
It will eventually heat up even at idle, and naturally will heat faster at higher RPMs.

My guess is that the hot water is not being pumped or thrown overboard as it should be.
When I touch the hoses that go from the thermostat housing to the exhasut elbows (that is supposed to make water go overboard i think) is relatively cool to the touch, which would explain why it's over heating
if hot water isn't expelled from system. Also, when we disconnect the hoses from the front of the manifolds (the ones that go from FRONT of manifold to thermostat housing),
and just let the water flow out, the boat doesn't overheat (even at high RPMs for extended period of time). So something is happening when water that is cooling manifolds goes back into housing that is causing it to over heat. Can anyone please help me out with what it might be?

Just in case anything doesn't make sense, it might not because I'm a complete amatuer mechanic so sorry about any confusion.

Thanks

Re: 1976 SeaRay with Mercruiser 233 (ford 351) is overheating

Raw water cooling system, not closed (if that helps!).

Re: 1976 SeaRay with Mercruiser 233 (ford 351) is overheating

Remove the exhaust elbows and see if they are plugged up. All water has to go through them.

Re: 1976 SeaRay with Mercruiser 233 (ford 351) is overheating

Thanks for replying!

I am pretty sure the exhaust elbows are not plugged up. We had previously removed them and dipped them in acid (forgot the exact name, but it had to be diluted in water and then let them sit in there for some time) to get rid of any possible rust or clogging. Also, I had forgotten to mention that when we unplug the hoses going to exhaust elbows from the thermostat housing, there is only cool water flowing out. This should have all the hot water going out right?

It seems that something is preventing the hot water that is coming out of the manifolds and going back to thermostat housing, from going back out to exhaust elbows and out of boat (also through housing). Does that sound possible?

Thanks again!

Re: 1976 SeaRay with Mercruiser 233 (ford 351) is overheating

I'd say the best thing for you to do is to take a picture of the engine from the top/front so we can see the hose routing you used. The routing on the 233/888 engines is a bit confusing in the stock configuration, so you may have the system closed off or plumbed incorrectly. One thing I'll add is that if the outdrive is still on the boat, you should be running water in through the outdrive. I would venture to guess that if you haven't been running the water through the outdrive, you've likely fried the impeller and possibly the housing as well.

Re: 1976 SeaRay with Mercruiser 233 (ford 351) is overheating

Thanks for replying!

I will take a picture of engine as soon as I get home. We tried following diagram exactly how it shows in book but we could have plumbed it wrong (it's an old black and white diagram), I'll post a picture later today.

Regarding out drive, we did remember to remove it.

Re: 1976 SeaRay with Mercruiser 233 (ford 351) is overheating

cvencebi said:

Thanks for replying!

I will take a picture of engine as soon as I get home. We tried following diagram exactly how it shows in book but we could have plumbed it wrong (it's an old black and white diagram), I'll post a picture later today.

Regarding out drive, we did remember to remove it.

Click to expand...

Perfect. Sounds like it will probably be a simple fix. I also assume that with the new thermostat housing went a new 160-degree brass thermostat?

Re: 1976 SeaRay with Mercruiser 233 (ford 351) is overheating

Yes we got a new thermostat. However we put it on backwards the first time, and then took it out completely second time, now we only have the top half so there isn't too much pressure (some guy at the boat shop suggested this, he said that regardless it shouldn't over heat. was he right?) Every instance it heated up. Damn now that I think about it I don't think we tried it with the thermostat in the correct position. I'll ask my nephew (sorry guys!).

Ok here are some pictures. I had my nephew send them to me so I can upload them asap! Unfortunately we left the hoses going from the thermostat housing to the exhaust elbows and from thermostat to the back of the manifolds (right under exhaust elbows but going into manifold) swapped in this picture. We had become frustrated and thought that maybe the diagram was wrong, and when it still didn't work we just covered it up and left. When I am able to I will swap them into the correct position (at least i think it's the correct position and upload more photos).

Here are the pictures...