Genset exhaust question

There is a piece of exhaust on my Halvorsen 32 that makes an "S" turn (stainless) as it exits the generator and lines up with the exhaust hose going from the generator to the port side exhaust. The stainless section has rusted through and needs replacing. My boat yard tells me that they are going to have to fabricate a fiberglass coupling ? to mate with the exhaust hose because Onan does not have a part that would do the job.
Has anyone had this problem and can it be fixed for less than the $1300 that I have been quoted? It just seems like it should be a less complicated fix.

There's ultra flex exhaust hose and/or fiberglass elbows that may work...

I would never pay $1300....I would use galvanized pipe and replace it every 2 years for less than $20 before I paid that.

Post some photos of what your are describing. Is the mixing elbow on genset still in good shape?

Is it sharing exhaust with the port engine, or just exiting on the port side. I agree, I would NEVER spend 1300 for that.

Shew....a lot of options could be exercised for less than that. What size is the SS tubing? You could weld a couple of SS elbows together. How tight is the radius?

Bill
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Thanks everyone. I will get back to you when I can get to the boat. Right now she is under about 6 inches of wet white stuff and too cold to go crawling around in the ER. I'll get some pictures as well.

When I installed a gen set in my boat I found all kinds of fiberglass elbows to use. I'm sure you can beat that $1300 price by D.I.Y.

You should be able to find the fittings you need at Centek Industries who manufacture VernaLift marine mufflers, fiberglass exhaust tube and just about anything else you would need for your project.

Larry

FG pipe can be cut at angles and glassed back together to make nearly any shape. Easy to do, and FG is better than SS in wet exhaust service. Wet exhaust is corrosive to SS. Corrosion rates depend on alloys and welding process used, and can be pretty quick.

I think the yard in China where the boat was built also produced stainless products which would explain the SS part of the exhaust. It didn't make sense to me on the wet side but that's how she was built. Definitely not going to replace with SS.

Bill Ranson said:

I think the yard in China where the boat was built also produced stainless products which would explain the SS part of the exhaust. It didn't make sense to me on the wet side but that's how she was built. Definitely not going to replace with SS.

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Stainless isn't inherently bad in that application...just should be a good grade and good welds.... and designed well.

psneeld said:

Stainless isn't inherently bad in that application...just should be a good grade and good welds.... and designed well.

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Yes it is.

Any austenitic SS above 70°C with seawater will likely fail. You might get by with a duplex stainless like a 2205. Hastelloy or Monel will give you longer service life.

Stainless is fine on systems that are well built and get used regularly. Cheaply built stuff sitting with stagnant water in it for most of its life can go bad quickly.

Properly welded (back gas/full penetration and passivation) produces exhaust components that can last a very long time.

Or you could use FG and be done with it.

I would go to a muffler shop and/or a radiator shop to have them bend the pipe and weld together. Last summer I had to have a tight 90 degree SS 1” pipe that a local muffler shop did it for free from some scrap he had left over. Two years ago had a radiator shop bend ½” SS for the 671, oil line, which they charged 25 bucks including the SS.

The yard said it would take several days and big bucks. Both times I went personally and talk/pleaded/begged the owners, willing to pay what ever the price, told them it was a emergency rush job, and anytime they are in the marina to come see the Eagle. Took less than 15 minutes and had the pipe back to the yard in 30 minutes.

RickB said:

Stainless is fine on systems that are well built and get used regularly. Cheaply built stuff sitting with stagnant water in it for most of its life can go bad quickly.

Properly welded (back gas/full penetration and passivation) produces exhaust components that can last a very long time.

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and that was really my point about being well designed...the total hours of contact are tiny on the average recreational boat...as long as the water doesn't sit in them...we have custom stainless injection elbows on the assistance towing fleet I'm with and they don't have issues as fast as the other materials..but then again...some of those are not put together well either.

I should add that I just recon'd my Northern Lights 4.5 genset which had a nice looking SS elbow that I assumed wouldn't give me any issues for a long time......NOT! When I did the recon, I pressure tested the elbow just in case and man....that thing was full of pin holes. Even after I plugged what I could find, it was just too perforated to spend any more time on it. The elbow looked just fine in and out. A lot of stuff can and does happen on the non-service side of the genset that I really got fed up with so I yanked that thing out from its impossible athwart-ships position under the galley and carved a new hatch in my veranda where I can now stand on either side of it. Soon, I'll have cameras there too.

Those of us with Krogens have become familiar with the behavior of SS in our boat applications, including the SS water, waste and fuel tanks that do a good job for quite a while, but sometimes suffer cracks from the lesser-quality welds, mostly due to the rods and techniques of the time not being able to absorb the decades of billowing of the sides from filling and draining tanks.

As a side, I certified in welding in Army Corps training in Ft. Meade in the 90's, and even then we were using exotic rods that did incredible welds on SS and even cast iron that varied in behavior and really needed to be "tuned" for specific applications. I don't think they did much of that in the 70's and 80's, and the base product of the various SS outside of the US, England, Germany and France (even specific grade) was pretty unpredictable in spite of the best intentions of the architects and contractors. I'm glad I don't have to be the guy who rates these materials. Ya gotta start with and weld with known materials. My opinion only.

Stainless is ok on the "hot side but anytime water can set in it you are asking for trouble. It should be insulated "lagged" to and over the hump, and water injected below that. Read Gerrs books, its a no brainer.