welding stainless exhaust box....

[Rockter]

I noticed today a wee line of bubbles coming out of the weld on the entry side of the stainless exhaust box on my olde ship. The motor is an MD17C.

I cannot face replacing the whole unit. Not right now anyway. I will buy a new exhaust box, and fibre-glass is attractive, but we will try welding first, if practicable.

The weld has gotten a bit tired. I had hoped to weld it in situ as the exhaust hoses will be very difficult indeed to remove... they were very difficult to get ON, some 12 years ago..... so is suspect I will tear something up trying.

It may not work, but I am trying only to re-establish the weld, and nothing else.

A guy I know has a welder and we could transport it the 90 miles to the boat.

Is stainless relatively easy to weld? I know we must use chrome-rich electrodes, but what else must we watch for?

Thanks.

[capttb]

I'm not a welder, but last time I had stainless repaired it needed to be TIG or MIG and was an effort to find a welder who could do the work & had time for a small job. Trying to weld in the boat sounds possibly hazardous. If it's just one tiny spot I might try something like J-B Weld (an epoxy) as a temporary repair.

[zz4gta]

What welder do you plan on using? How are you going to weld it?

TIG and MIG are very common. After setting up the stinger, a monkey could MIG weld. However, I'd highly suggest removing it from the boat. If that can't be done, have a "buddy" with a fire extinguisher at the ready. And make sure you have a fan running to keep fresh air coming in. Gases from welding can kill you.

[zz4gta]

A slower approach may be to try and use a small oxyacetylene torch. You can pick them up at some hard-ware stores.

[jrd22]

I would guess that if the weld is starting to leak it is probably at the edge of the weld and that area might be very thin. Usually by adding more weld you will burn thru, or just move the crack further along. To do it right you should probably weld the leak and then grind it down and weld a plate over the top which will probably require taking it out of the boat. Sorry, I know you didn't want to hear that. If this is a short time fix, you have nothing to lose by trying to simply weld it, but I'm betting it is on the underside (hard to get to) of the pipe and it will be difficult to do a good job of welding.

Good luck, John

[pfatyol]

I teach welding at a local Vo tech from time to time (full time Manufacturing Engineer). Even though SS is easier to weld than steel, there are a few things to watch out for. Filler material, if box is 304 or 303 your going to want to use 308, but if it is 316 then 316 will be preferred. I have never attempted to stick weld SS, I always have used Tig or Mig. In which the argon is heavier than air so be careful. Additional if you have too much airflow through the engine compartment you'll blow the shield gas away and contaminate the weld. The weld will be much more prone to corrosion.
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I would strongly suggest removing the exhaust box off and dropping off to be rewelded. With a box on the bench it would be far easier to get proper bead laid depending upon the conditions. We Tig weld SS that is .020" without burning through. A local Vo Tech welding class might be willing to do the job for free or for a small fee.
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Good luck,
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Patrick
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[Rockter]

Guys...
Thanks.
To get it off the boat will mean either cutting the exhaust pipe between engine and exhaust box, or taking off the exhaust elbow. I was anxious to disturb as little as possible.
I had a look at the Vetus website today. perhaps I should fit one of their new exhaust boxes....?....

Welcome to Vetus.com!

...page 145 or thereabouts, and they are not wildly expensive.

Shame top dump the current box, but it looks like chlorine has had a go at the weld.

[Valiente]

I went from an Onan "pot" type waterlift muffler to a plastic Vetus "waterlock". It was awkward to get at, but it was a huge improvement as the Onan was crumbling on the inside and letting water backsiphon into my Atomic 4...bad, bad.