Catalina 27 Part II

[joe_db]

Anyone know what happened to the first post where it is closed?
Also it does not look like a normal A4 flange on the there either. Is that an odd version of it or ????

[Dave Neptune]

Looks like a "union" on the end. I'd try opening the union and replacing the "half" with the nipple in it. Then replace the nipple and retighten the new union half. However since the exhaust is over 3 years old probably replacing it would be a better idea.

Dave Neptune

[hanleyclifford]

Anyone know what happened to the first post where it is closed?
Also it does not look like a normal A4 flange on the there either. Is that an odd version of it or ????

I've never seen a flange like that but would love to hear about it. I don't like the union in the exhaust riser. The idea of a union is to make partial disassembly possible but in this environment I cannot see that as possible or beneficial. The union also reduces the cross sectional area available for exhaust flow, and in a 1 1/4" system that is not to be squandered. For most of us an exhaust riser needs to be seen as an expendable unit in it;s entirety although it is possible to assemble black iron less than "pipe wrench tight" and have a prospect of reusing at least a flange. Fore and aft, and athwartship support is necessary for our risers.

[ndutton]

From the original post:

Also, the strut/support from the transmission to the upper loop of the hot section had not been reconnected when the marina replaced the engine in 2011 when I bought the boat - a forum indicated it wasn't necessary, so I did not replace the strut in 2020, which may be why it has recently failed(?).

I think you hit the nail on the head here. After only 3 years I don't expect this is a rust-through issue but rather a stress failure from a combination of vibration and leverage. It's your first hand experience regarding the importance of the support of the heavy hot section despite what the lazy marina mechanic or some forum keyboard expert might have said.

As for the union in the system, I'd be more concerned with it adding a restriction than anything else.

edit: further research stumbled upon what appears to be the unusual (to us) exhaust flange:

https://www.catalinadirect.com/shop-by-boat/catalina-27/engine/exhaust-system/engine-exhaust-flange-kit-for-universal-5411/

[hanleyclifford]

https://www.catalinadirect.com/shop-...niversal-5411/ So does anyone know what the extra little tab is for?

[joe_db]

FYI, this is a 5411:

[ndutton]

The OP said it was a 5411 in his opening post of the now closed thread. No problem using an MMI hot section for another engine but it may also explain why the support strut is so important for his shaky diesel. As for the flange ear, it's typical of Universal for their later exhaust manifolds to have the water jacket open at the exhaust end. The ear, also covered by the gasket, seals it off.