Dry exhaust pipe section

[redbopeep]

I'm both confused and a little frustrated. We need a 21" section of dry exhaust before the water injection elbow. The manifold from the Cummins engine has a threaded (2.5") output and I've got a carbon steel "unique" flange that the previous owner had welded up with a nipple that threads into this manifold. Clearly, I can just thread straight into the Cummins (if the exhaust hangars allow movement with expansion/contraction of the dry section as it heats up and cools. Or, I can get more standard flange...

Thought that this obtaining the piping would be fairly easy and straightforward since I'd heard that one could just use "black iron" plumbing pipe and super insulate it w/any number of things.

Well, you all probably know this (but I didn't!) "black iron" that's real iron isn't suitable for the super high temperatures of exhaust gas exiting the manifold. The stuff they sell these days and call "black iron" is simply steel anyway...

So, I'd also "heard" somewhere that one didn't want to use stainless steel pipe in this hot area off the manifold. Hummmm. I can FIND stainless steel (316) but can't recall why one might not wish to use it.

Does anyone have a dry (not water jacketed) section of exhaust? If so, what's it made of? How is it insulated? How does it deal with thermal expansion (flange system for expansion OR sliding w/in hangars?).

thanks!

[ssor]

Your cars and your trucks have either stainless steel or they have cast iron exhaust manifolds. The exhaust pipes are usually steel. Viewed at night when run at full throttle these pieces will sometimes glow red hot. The local watermen with there work boats and truck engines just shield the exhaust from contact with people and put mufflers on.

[Canoeyawl]

With a rigid mounted engine (different than a car or truck where the entire exhaust system is allowed to flex with the engine)
a short flex type stainless coupling pipe is common. These are available $$ with pipe thread on each end.

[Jim Ledger]

I had a boat with a dry stack that came out the back of the exhaust manifold and turned 270 degrees to go through the cabin roof. It was made of "black iron" (steel) pipe and fittings, 2 1/2" dia. wrapped with asbestos tape.

This was common practice for the type of boat and seemed to work just fine. At one point,I changed the exhaust to exit from the front of the manifold, removing the old pipe, and I recall the pipe being quite strong. These stacks were about three feet long, with an automotive muffler outside the cabin roof. The mufflers needed periodic replacement, but the pipe never did. They were also totally unsupported by anything other than the exhaust flange of the manifold.

[The Bigfella]

Mine has flex pipe - which I assume is stainless. I had new insulating blankets made up for it when I got new mufflers.

[Gary Bergman]

I had to do some minor adjusting last summer after changing engines on the run. Now the dry leg of mine is both stainless(6" piece), and iron (the rest). No problems so far, pushing her lotsa times..

[redbopeep]

I'm feeling a lot less concern about the material. Seems that either the black iron (steel) pipe or the stainless would work. I'll just see what I can get at the right length.

In addition to the manifold connection, hubby had planned on placing a tube mount with tripod (lower two legs to the engine mount brackets upper to the manifold). Sounds great for allowing for expansion of the pipe. Don't quite know how I'll properly insulate around it. Did I mention one part of this dry exhaust is just two inches from the (wood) chart house sole?

Thanks for the info on what you'all have.

[ssor]

Just slip a sheet of steel or aluminum between the hot pipe and the wood with good support on the sheet and free air flow. For just avoiding people contact with the hot pipe, expanded steel mesh will be adequate.