How to repair corroded flange in stainless wet exhaust?

[Captainlabrador]

Hello,

I'm pretty new to boats & engines but I've got a Volvo 290 - a 6 cyl. diesel in a 44 foot cruiser (homebuilt by someone else back in 1987).

The exhaust has a leak - the flange on this huge stainless steel exhaust pipe is corroded right through. It is a "wet" exhaust - the cooling water goes from the engine int the exhaust.

Anyway - I'm looking for a good way to fix it, but can't find any similar systems on line.

Aplogies if this isn't the right place to ask ... it isn't really a "design" question.

[Guest62110524]

hi
ss hates warm salt water
you need post a pic
Looks like you will need machine up a new flangle from 2205 which has good corrosion props and high tensile strength(not that you need high tensile at all) post a pic let's have a look
you could make up a pattern have it cast in gunmetal, which would last 1000 years or just fabricate one from a high grade pipe steel and coreten last another 15 years

[Ad Hoc]

Capt.L.

Since the exhaust is already S.Steel, do you know what type it is? As this will affect the repairs service life. If it is lesser quality, it may mean a totally new exhaust; since to weld it with a patch, if that is what you are intending to do (depends upon the size of the penetration), may cause more problems than it fixes.

[Captainlabrador]

Thanks for the replies.

Here are a couple of photos.





The problem is that the flange on the left side has a hole corroded around about 40% of the "neck".

I've taken the exhaust out of the boat & the photos show it upside down compared to how it is installed in the boat.

The exhaust is connected to a Volvo Penta 6 cylinder diesel I/O - model 280 or 290. Boat was built in mid 1980's.

I'm hoping someone can recognize the exhaust system so I can find the company that made it and order a new flange and have it welded on.

Otherwise I'll try to fix it with high temperature JB Weld.

[Captainlabrador]

Oh ... another thing - I've got the boat on Great Slave Lake - so salt will no longer be an issue, although it had been down to the Bahamas before I bought it.

[Guest62110524]

strange how that got like that, , its , by way pipe spigot, not a flange, thats why needed pic
Is water injected into the pipe downstream of the jacket? looks like that was the case You are often better off with steam pipe than ss, as when you make that lot up in ss you nneded flood the thing inside with argon, or crevice corrosion occurs SS, as I said is rubbish on exhausts Anyways you have two choices, take of the last piece of jacket, weld a new inner pipe on, and then replace the jacket, or remake the lot in copper, or steel, I hate that sorta work, good luck mate
oh seeing as you are now in fresh, you could fab it all in steel and galv it

[CDK]

For a construction from the mid 80's to show some corrosion isn't unusual. If it would have been any other material it would look much worse or had already been replaced a few times.
Yanmar uses thin walled stainless steel for the first part of the exhaust on their small diesel engines: that also survives approx. 20 years.

The cause of corrosion in that particular spot may be contact with a different metal. The stainless part survives longer if it is electrically isolated.

Only exotic materials like tungsten and titanium can endure hot seawater almost indefinitely but the cost is of course prohibitive.

[Frosty]

What I see in the picture is typical and Im sorry is junk. Remake the pipe and possibly improve on its design and make it bigger , it looks a bit small dia pipe for a volvo 6 cylinder.

After water injection the pipe should be doubled in size.