Soot exhaust leak

You could get a point and shoot thermometer. Set a base line, compare P and SB. Check them once in a while at similar operating temps. If it starts getting hot around the edges of the insulation or develops (much) hotter spots you can assume something's going on in there....

Was working on my Yacht today ...40 year old Ocean Yachts that is .
Took the semi-soot stained blanket off my Dawg and was able to pull off chunks of old iron from the bottom of the original J&T cast below at the round flange connection to the Turbo exit side .

Do you think it's time I change it out ?! 40 year old elbow.
Yes I did the starboard side three years ago.
My boat is a restoration in use vessel. Keep on using it and replace things as I go along. I love it

Thanks. Will do. I used to casually inspect the systems. I will now examine them more closely. Thanks Dan for raising the issue.

Yes, replace. If you're getting soot on the blanket you have an exhaust leak. If chunks of old iron are falling out of the cast elbow, it's shot.

I'm also a fan of the "if it ain't broke..." principle, generally speaking.
But removing the shrouds after 22 years for a decent visual inspection sounds pretty reasonable, to me.

Beau
Are your risers cast iron or stainless?
I've always noticed nice stainless cans on the MANs.
You may see a water leak before an exhaust leak with the shinny dawgs.

Chunks of iron or just bigassed rust flakes?
I remember a member a while back that replaced a iron mixer with the updated stainless unit but had a hose connect problem. Before you take it apart, take a bunch of pictures to your J&T shop to make sure it's a real plug & play.

They are stainless and I see nothing evidence a leak.

These guys make a replacement in cast stainless steel elbow that looks much superior to the original cast iron or a welded stainless mixing elbow and very inexpensive compared to the competition. https://hdimarine.net/

On their opening page they are showing bronze elbows for a SS mixer, Is that good? Mine are all SS, if my memory is correct.

I'm not the expert there but it comes with a real thick gasket and I don't think that joint is wet except when running. I do share your concern and wonder why that part is not stainless. Probably worth asking their opinion and others on yachtforums will likely offer advice.

Yours was made for your engines with the boat install in mind. All custom welded stainless.

HDI makes replacements without any custom thoughts. Including not knowing what hose size will be used at the dump can or what direction the hose needs to be pointed.

Bronze will work just fine with the cast stainless.

good to know

What's a dump can? Other than the one we all already know about....
What's it purpose such as inline DD71s? and others?

Far from an expert my understanding is that the main function of the dump can is to cool the exhaust gasses so they can pass through the fiberglass tubing and “rubber” hoses as the exhaust exits the boat. I replaced mine as the yard was in there doing major work and the yard said the spray ring holes were becoming corroded. They said I had about 5 more years but I replaced them since access was available. I never saw any evidence of soot on mine.

Ok , so all combustion gas is passed through the turbo and out the elbow? With the elbow being water jacketed with a ring collar with holes in it spraying at the exhaust gas after the turbo within the elbow... ? This is where all the the cooling water comes from out the stern exhaust pipe ? The only source of water out the exhaust pipe ?

I do know if the elbow cooling water holes get clogged up you can have a big problem and or fire from all the heat generated there.

Usually before the hoses and tubes start melting and burning, somebody noticed the engine temp going up.
If raw water does not go thru the whole engine systems, it over heats.
This is the big question if water is coming out your exhaust, one; pumping water? two; pumping all the water? If the riser, mixer, dump can is restricted, the motor gets warm/hot/overheats.

Check out the website at post # 29 for a visual of a replacement set up?

Nope. The main function of dump cans is to silence the exhaust.
The possibility to use rubber hoses after the dump can is just incidental, sort of.
In fact, also u/w exhausts (where there's no can) have at least one section made in rubber, to avoid transmitting engine vibrations to the hull.
Of course, that can only be done after the raw water re-injection point, because the initial dry section right after the turbo can get red hot.
Which is the reason why it's covered with insulation, but that applies to both u/w and can exhaust systems.

Are you referring to a water-fall or flooded muffler can? Confusing it with a riser/mixer/dump can?