Exhaust - Need to insert a 90° elbow between exhaust mixing elbow and muffler

[TCL]

I had to replace the exhaust mixing elbow on my Perkins 4.236 and the new elbow from TAD has a slightly greater down-angle than the previous (no longer made).

Previously, the connection between the mixing elbow and the Centek muffler was made with regular black hardwall wet exhaust hose. But the new turn radius is too much (or too little, whatever) for the hardwall hose. (And softwall wet exhaust hose collapses.)

I understand that Trident makes high-temp silicone hose with bellows, as well as high-temp silicone hose already formed into a 90° elbow. But I'm inclined to use a 90° pipe, connected to each of the mixing elbow and the muffler with a straight piece of black wet exhaust hose, unless convinced otherwise. (So mixing elbow > exhaust hose > 90° elbow (metal) > exhaust hose > muffler.)

Any reason not to do so? Any thoughts on cast iron versus cast stainless versus carbon steel? I realize that cast iron will be more prone to corrosion. If looking for cast stainless, is there a certain type I should look for?

Any other options I'm not thinking of to accommodate this tight turn radius between the mixing elbow and the muffler? Thanks in advance.

[Cheechako]

I think the more flexible one piece silicone unit may have advantages over a multipiece system with many clamps etc.. But hard to say without seeing the system.
Is it a very short length to fill? or like a foot+?

Apparently the water is mixed prior if you had exhaust hose. If that is correct, then there are fiberglass exhaust elbows available avoiding metal altogether.

If going metal I would probably just use a cast iron/ black iron elbow, it holds up very well in exhaust. SS can be a turkey shoot for longevity.

[Jeanneau 45.2]

LIKE THIS:
https://marineengineparts.com/centek...st-elbow-3-90/

[FPNC]

Avoid a hard 90° if at all possible. Use two 45° elbows or possibly a long 90° 'sweep'. Elbows can be rubber, stainless steel or fiberglass.

[JD-MDR]

I just moved mine over about 12" for better access to my water pump, fuel filter and gearbox dipstick. It was on top of the reverse gear connected directly to the mixing elbow I Made a FRP fitting to use a minimum of clamps.. I didnt realize how many factors there are to consider to have proper setup . I think it's OK but would appreciate any comments. This photo is missing some clamps. The motor is MD7A
with v-drive. So the muffler is now under the galley sink. I had to remove it everytime I wanted to service water pump etc.

[Sailmonkey]

What about corrugated hardball hose?

Vetus slang is really flexible

[JD-MDR]

Originally Posted by Sailmonkey

What about corrugated hardball hose?

Vetus slang is really flexible

Yea. Someday I'll get the flex hose but that's another $500 and for another day

[JD-MDR]

Originally Posted by JD-MDR

Yea. Someday I'll get the flex hose but that's another $500 and for another day

Oh, I made sure about half of the exhaust hose( from the bulkhead) has a continuous slope back to the muffler . The aft end slopes slightly back to the stern then drops down to the outlet

[stormalong]

You can make your own fiberglass elbow to any angle you want. I did this over 20 years ago to reroute my exhaust hose. You can buy the Centek fiberglass tube in three foot lengths. Cut multiple wedges to form the angle you need. Epoxy the edges together. When cured wrap the hole fabrication in multiple layers of epoxy saturated fiberglass mat. Incredibly strong - still in use today.

[JD-MDR]

Originally Posted by JD-MDR

Oh, I made sure about half of the exhaust hose( from the bulkhead) has a continuous slope back to the muffler . The aft end slopes slightly back to the stern then drops down to the outlet

The muffler is about 7" below the water line .. It was right about at the waterline before. There is so many different diagrams on how to set up

[waterman46]

I had exactly the same issue on my 4.154. The new mixing elbow angle is just a little in the wrong direction. In Costa Rica at the time, I used a standard pipe elbow (sorry can't remember the size) with pipe nipples on each side of it. The OD of the nipples fits into standard exhaust hose ID quite nicely. This will need to be replaced every 5 years or so. The can't be separated after a few years of use, so you need to carry spares for both the nipples and the elbow.

The new owner had a special swept elbow made from SS. You can go that route, it's not all that expensive.

[waterman46]

I had exactly the same issue on my 4.154. The new mixing elbow angle is just a little in the wrong direction. In Costa Rica at the time, I used a standard pipe elbow (sorry can't remember the size) with pipe nipples on each side of it. The OD of the nipples fits into standard exhaust hose ID quite nicely. This will need to be replaced every 5 years or so. They can't be separated after a few years of use, so you need to carry spares for both the nipples and the elbow.

You can special order bent SS pipes in these sizes. They are not all that expensive, I had to get one to do a head outlet installation.