'96 Supra TS6M right side Exhaust overheating

I am new to this forum and have searched for a similar problem to no avail.

My 96 ts6m has the right side (if looking at the engine from the rear) exhaust overheating.

The left side exhaust is cool while the right side is getting very hot. To the point of smoking.

I have pulled the raw water pump lines and water is making up from the pump and out to either side of the exhaust manifold.

I pulled the Raw water pump and looked at the impeller through the hose holes and all the arms are there and it looks good.

It seems like there is an imbalance of pressure causing all the water to go into the left side manifold.

I even pulled off the right side exhaust riser, but I do not know what I am looking for.

Any thoughts?

I have not pulled the boat from the water yet so I cannot tell if water is making it out of the exhaust flappers.

Show us a picture of the inside of the riser and manifold where the riser bolts on.

The inside of the exhaust manifold may have rusted through internally?

Here are the pictures of the manifold and the riser:

https://drive.google.com/a/sealedmin...9sV2tkUUU/view

https://drive.google.com/a/sealedmin...hWekR4MUU/view



If rust is the problem can I just take a bore brush and brush up the inside, therefore opening them up?

Firstly welcome. I find this forum and the guys on it fantastic. Everyone is helpful and plenty of information available. If one side is overheating then I would think there is a blockage somewhere. I don't know if the 96 has rubber exhaust hose after the riser. If it does I would disconnect and see if water is coming through.

Is this a PCM GT-40 engine? edit: I see from the valve cover that it looks like a Pro Boss / HO ... some variation of 351. Neither here nor there, just confirming that it's a "Ford."

I had a similar problem a few years ago but it was only after idling for long periods of time. You can read all about the saga here: https://forum.supraboats.com/showthr...-hose-overheat

But one thought I had was that after getting hot once or twice, the 3 1/2" hose itself was collapsing internally and sealing off the water port on the manifold, not allowing water to pass through efficiently. However, this turned out not to be right. Or at least, not the whole problem.

What I would do in your case is remove the whole manifold and riser from the engine, then thoroughly flush out both and reassemble. Minimal cost - the gaskets are cheap. This will eliminate the possibility of rust buildup causing a blockage in that assembly. In that process you'll have to remove the hose from the thermostat to the riser, which is good to check out too. Maybe there are some old pieces of an old impeller in there?

Be mindful of the location of the closed port on the manifold-to-riser gasket, it goes toward the stern which forces water to go up and over the riser rather than up and straight down through that 'easiest path' on the rear, lowest part of the riser. Where was that closure when you took it apart just now? It looks like it was correct in the pics. But once you clean off all the old gasket material, it can be hard to remember.

Are Both exhaust pipes the of all debris. Could One of the mufflers is slightly plug. If there's more exhaust pressure on one side and the other it will force more water to go through the free side.