Having an overheating problem.

[BP88]

I acquired my boat at the end of last Summer. At the time it was given to me it had been sitting for 10 years in a barn and the engine was taken apart. It had gotten hot and blown a head gasket and they never did anything with it.
Anyway, with a lot of help from everyone on these forums, I rebuilt the engine and actually got it wet last September. Unfortunately I couldn't get it to run and ended up having to rebuild the carb over the Winter.
However this year I finally got a chance to put it back in the water with the rebuilt carb and was able to start it. It does start hard, (have to prime it several times), but that's another issue. Once I get it running, it flat out runs great. The problem is that I can only go about 1/2 mile before I have to shut it down because it's getting too hot.
My setup is as follows: Harmanized Ford 460 with a Berkeley Jet.
Right now the water inlet off the jet goes to a T, then a hose goes to each side and into a port on the front of each Harman header. Then it comes back off each side through a port right next to where the water goes in. From there each hose goes to a port on each side of the Harman plate that covers where a water pump would go on a normal engine. Then there are 2 water outlets coming out from where the thermostat would go(mine has no thermostat, just a plate that covers the water hole). Then those 2 hoses go to each side and onto outlets on the back of each header, then exit the system. There are 2 ports where hoses would go onto a spacer that the carb goes on, but they weren't in use when I got it, and looked like they hadn't been in a long time. Besides, I know that wouldn't cause the engine to overheat. I include this info because I had to put everything back together and am not positive that the hoses are routed correctly. I am 90% sure it's right based on the fact that they really won't fit any other way based on their lengths. And the fact that if I hook up a garden hose to the inlet water does circulate through the system and come out the exhaust port.
I installed a simple on/off garden hose shut off valve between the inlet hose coming off the jet and the hose that connects to the T. So I can shut that valve and run the garden hose through the engine while the boat sits in the water and the engine is running. If I do that the engine does not get hot. But if I hook it up normally and run it, it gets hot. I can take that plate off where the thermostat would go and water barely bubbles out while the engine is running. I would think the water would gush.
I do know that there is no obstruction in the hose coming off the jet because I can open that valve while it sits in the water and water comes rushing in.
Based on all this I have my theories. I think that maybe the wear ring on the jet is worn and the tolerance is too big to push water into the cooling hose. Instead it may even suck the water out, I don't know. I had a boat mechanic tell me that if the wear ring was that bad that the jet would cavitate and that it wouldn't push the boat, at least not fast. Well, that isn't the case.
Am I on the right track here? It is true that the only thing pumping the water is the jet itself correct? There is no water pump.
Instead of rebuilding the jet, should I try installing some kind of auxiliary pump and put a new hole in the transom to pull that water in?
Sorry for the novel but I wanted to make sure I provided enough info.
Any help would be greatly appreciated.

[HBjet]

Have you tried disconnecting the hose from the pump, and just hook up a garden hose while the boat is on the trailer with the motor turned off? Just turn on the hose with a half or 3/4 turn and water should go through the motor and then come out the exit line. If you do this and after 15-30 seconds you don't see any water comming out of the exit line, then you have a problem in the plumbing that needs to be addressed.
Yes, the motor only get's it's water off of the jet pump, which supplies enough water.
HBjet

[Floored]

when the engin is running in the water the pump should definately pressurize the cooling system. on my boat I have to bleed air out of the pump when i launch it or I get an air lock and mine will overheat. it will still go but it just wont pass the cooling water. It sound like you have all the hose hooked up right and water through the garden hose eliminates a blockage so try to put it in the water and open the valve enough to bleed all the air from the pump then start it and see if you get your water flow its worth a shot worked for me

[BP88]

HBjet:
Have you tried disconnecting the hose from the pump, and just hook up a garden hose while the boat is on the trailer with the motor turned off? Just turn on the hose with a half or 3/4 turn and water should go through the motor and then come out the exit line. If you do this and after 15-30 seconds you don't see any water comming out of the exit line, then you have a problem in the plumbing that needs to be addressed.
Yes, the motor only get's it's water off of the jet pump, which supplies enough water.
HBjet Yeah, I can run water through it when it is just sitting on the trailer. It comes out both exhaust ports.
That is why I assumed I had my hoses right.

[Moneypitt]

Any chance the wet logs are leaking exhaust gases into the wrong section of the manifolds? Everything else you've described sounds normal, so this is a long shot but the exhaust pressure COULD be stronger than the jet water flow comming to the engine thru the logs. Your set up is standard plumbing, but I've always ran the water from the jet, to the T, into the engine at the front, out the top, into the exhaust log, out of the log, and around to the rear of the system to exit. This bypasses the idea of heating the water prior to entering the block and allows the engine to run very cool, sometimes to cool, thats why some boats,(most) are plumbed to preheat the water. Are you sure the head gasket is fixed, is the head(s) cracked? ONE more thing, look at all your plumbing, and fittings. What size hose comes off the jet, and what size are the splits after the T. Are there any fittings in the system that may have a reduced ID? Has anyone checked the flow thru the exhaust. AANNDD finally, what type of gauge are you using to show the temp? Does the water exiting the block feel hot? Feel the hoses and try to determine when the water inside the hose is hot, how hot does the gauge say the engine is before you shut it down...just shots in the dark.........Moneypitt

[TX Daytona]

I would also try taking the hose, from the pump to the T, off at the T, with the boat in the water and fire the engine for a short time and see if you have mucho water shooting out of that hose. Then, at least you know for sure your pump is putting plenty of water to the T.

[BP88]

TX Daytona:
I would also try taking the hose, from the pump to the T, off at the T, with the boat in the water and fire the engine for a short time and see if you have mucho water shooting out of that hose. Then, at least you know for sure your pump is putting plenty of water to the T. This was the one thing I did think of that I didn't try. I just ran out of time on Sunday and had to get the boat out of the water for the weekend to make my 3-hour drive home.
If it isn't coming out with real high pressure, then would my theory about the wear ring have any credence?

[Hallett19]

There is a good chance that if the hoses are setup right, you might have some sand in the block or a blown headgasket. Pull the motor high enough to get a freeze plug out, shouldnt take you that long with a cherry picker. See if there is a bunch of sand in there, if there is, you probably just found you problem. Blown headgasket too, pull the heads, check all the gasket around the water passages, if there are any breaks, there is the problem. Good luck !