Hi all,
I have a Westerbeke 35B diesel engine with the usual heat exchanger and exhaust elbow with raw water injection system.
Since the engine is approaching 1000 hours of operation, I decided to pull the exhaust elbow for inspection and testing.

As the pic (of the manifold end) shows, the elbow is heavy gauge stainless with extensive lagging covered by aluminium foil to minimise excessive heat in the engine bay. The elbow connects to the engine manifold by a cast iron threaded flange which screws into the elbow.

My main concern was leaking of exhaust due to corrosion of the elbow primarily at the point where the raw water injection occurs.
Happily, there was no significant corrosion at this point, but a pressure test showed significant leakage via the threads of the manifold flange.
So, to my question - assuming I can unscrew the flange, what can I use to coat the threads and seal the exhaust leakage?

regards to all
Allan

The cast iron bit is sacrificial. The idea being that it's cheap and easy to replace versus the nice SS bit. Poke at the cast iron with a screw driver to see if it's still solid. If the screw driver goes through then replace. If it's solid and you can unscrew I would just put it back together with RTV silicon on the threads. High temperature RTV.

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Ramona said..
The cast iron bit is sacrificial. The idea being that it's cheap and easy to replace versus the nice SS bit. Poke at the cast iron with a screw driver to see if it's still solid. If the screw driver goes through then replace. If it's solid and you can unscrew I would just put it back together with RTV silicon on the threads. High temperature RTV.

Thanks Ramona - much appreciated.
Looking at High temp RTV specs, it's good to around 360 C.
I've got no feel what is a typical manifold outlet temp in this application - what do you think?
regards,
Allan

Stag Jointing Paste is highly recommended in that application.

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cisco said..
Stag Jointing Paste is highly recommended in that application.

Thanks Cisco - good thought

Another option would be the paste used to seal exhaust manifolds to engine blocks - very high heat at the manifold. Paste is called "Maniseal" and is quite cheap from auto stores.

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Karsten said..
Another option would be the paste used to seal exhaust manifolds to engine blocks - very high heat at the manifold. Paste is called "Maniseal" and is quite cheap from auto stores.

Thanks Karsten, that's worth checking out
regards,
Allan

+1 for maniseal, I use it for a small diesel tractor engine.

Ahhh well, it's all academic now. I tried to unscrew the flange ....
I suppose it wouldn't have snapped like it did if it hadn't become brittle over the years of operation.

Now I need to locate a replacement exhaust elbow for a Catalina 34...
Any suggestions will be gratefully accepted....
regards,
Allan

I would just rip of the lagging to check the condition of the rest of it and either weld up the SS bit with a sleeve or make a new one altogether. It looks like it has failed where the salt water meets the hot exhaust. Probably only a short piece welded in would suffice.

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Ramona said..
I would just rip of the lagging to check the condition of the rest of it and either weld up the SS bit with a sleeve or make a new one altogether. It looks like it has failed where the salt water meets the hot exhaust. Probably only a short piece welded in would suffice.

Worth a try Ramona, I'll keep you posted....