Help! water flowing problems

First off, I work on cars. I understand engines, have built engines, and know the internals of engines. Transmissions.

I'm lost on this boat that I have just purchased.

I bought a jet boat, with a 351 ford engine, and one side of the exhasut continues to burn through the exhaust hose. I've replaced it 3 times, everytime it burns through.

I'm trying to figure this thing out, but I'm lost on how the coolant runs from the lake, to the engine, to the exhaust in 2 places?

From what I saw:

1. nowhere is there a fresh water pickup for the engine in the first place, I didn't see anything on the jet drive, but I'm going to look again today. ( I know there is one!)

2. There is a hose on the water pump bottom, (normal cool water pickup on a car) that goes to a metal canister, that branches off 2 seperate lines that goes to the manifolds, 1 one each side.* (see next)

3. On the end of the manifold, there is 2 lines (water hoses) going to each manifold. The lower hose goes to the waterpump, and upper hose goes under the engine, and I haven't found the source yet. I'm looking tommorow. (must be the sorce for engine coolant)

4. From the thermostat housing, I have 2 more hoses that branch off and each runs to the discharge end of the exhaust riser. I guess that's the discharge for the hot engine water.

5. With the engine running, I can take off the lines off of the discharge of the exhaust riser, and get no water. Of course, if there is a thermostat in the engine, then I shouldn't have any water cause it wasn't up to operating temp yet.

I'm lost fellas, any help will be greatly appreciated!

David Moss

 

There should be a bypass at the thermostat or the housing. Marine engines always have some flow to keep the exhaust cool. There may be corrosion blocking some of the passages.

 

investigating

I've found the cold water pickup, which is inside the boat, right into the jet.

The hose runs into one of the fittings in the end of the each manifold. The water then runs through the manifold, then comes out the other fitting, that leads to the water pump.

I'm going to take the boat to the pond tommorow, and run it with the hoses off the ends of the manifold.

If I get cold water from the jet, then I'll hook them back up.

Then, I"m going to crank it up again, and if I get water from the water jacked headers, then I"m going to hook those hoses up to the water pump.

Then I'm going to pull the thermostat, and see if I can get a steady flow of water to the outlets of the hose that goes to the heat riser. (also inspect the thermostat)

That should let me know what it going on.

Thanks

David Moss