exhaust smoke
 

1987 Supra w/V8 351

The problem is the final exhaust hose after the riser is smoking...Here is where I am at.

There was smoke coming from the exhaust manifold at first so I ordered a new gasket for the manifold and a brand new manifold just in case I needed it. The manifold gasket was junk along with a few bolts that had to be cut out. So I changed the gasket(also change the valve cover gasket). Now the the big hose is smoking and not the manifold.

And it doesn't start smoking right off the bat it starts after running for several min. I look at the back two baffles and an even flow of water is coming out of both. I unhooked the hose from the riser and there is no blockage.

Should I just get a new hose? Or is there something else I should be looking at?

how hot is the riser? is the hose smoking because its hot? shouldnt get near that hot

The riser gets warm. I could probably keep my hand on it for a couple seconds before I'd have to take it off same level of hot for the hose maybe a little hotter. But it's not like if I touch it I'll get burnt right off the bat.

It almost seems like there is oil or something on the hose and then when it heats up it starts to smoke. But that doesn't seem to be the case.

but it is hotter than the other side? they should run the same temp. and the hose shouldnt be any warmer than the riser. but you say equal amounts of water are coming out of either side?

right equal amounts of water are coming out the back. And no I don't think its hotter than the other side. If the hose is hotter its just barley. Could it be getting hotter because I'm running it on a hose and its not getting enough water?

is there just oil on the hose?

no

Like smoke coming out the exhaust flap or off of the outside of the hose?
If it's out the exhaust flap, maybe, older boat, burning a little oil on that side of the engine.
You checked for blockage, did the inside of the hose look smooth, not overheated and burnt?

its coming from the outside of the hose not the flap. I'm no expert but yea the inside of the hose looked fine.

Maybe a small crack or something and the smoke is real steam?

I wouldn't dismiss the fact of age/temps/materials! 25 years can make almost any material impervious to the elements, what's the question, replace both exhausts before you blow up!

the question is do I go replace the hoses or is there something else it could be that I should look into.

Ok so today was a nice day without wind so I could tell exactly where it was coming from. The smoke is coming from hose just after the riser about were the clamp is for the riser. And most of the hose isn't hot at all but right where the riser is its real real hot. Move down the hose 6 inches and you can keep your had right on the hose no problems.

I got the riser off lastnight. Now what am I looking for to tell if I need to replace it. I will say that the very "end" of it where the water and exhaust meet its very black just like the inner exhaust chamber. Should there be this much carbon build up? Also I noticed that on the hull where the water blows out there is a carbon build up on that as well but just the one side.
Is it time for a new riser and all my "hot" problems will be solved? thoughts?