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Old 06-04-2015, 07:39   #1
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Wet exhaust- which metal?

Hi. I have a westerbeke w13 which cracked the wet exhaust elbow. I have since bought a new one and am having a lot of fun trying to get the old elbows and couplers (nipples) apart. My question is what metals are acceptable to make this out of? Currently the elbows are 304 stainless steel and do not look corroded. The couplers I do not think are stainless as they are quite rusted and seized to the elbows and manifold exhaust flange (penetrating oil, heat gun, bench vice, and a large wrench) . At the hardware store all I could find in the 1.5 npt inch size are galvanized steel. I don't want to use this. At west marine I can find brass (yellow) couplers and elbows. They are expensive but available. I have no idea where to look for stainless elbow and couplers/nipples. Anyone have a reason why I can't use brass other than cost?
If I should use stainless steel any idea where I can get the parts ? Also what about using brass nipples with stainless elbows? Will those metals seize together?
Thanks
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Old 06-04-2015, 07:57   #2
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Re: Wet exhaust- which metal?

Try a hydraulic hose & fitting supply
Brass should be ok but can suffer from
Losing its zinc needs to be checked from
Time to time but would expect it to last
at least 2 yrs
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Old 06-04-2015, 07:59   #3
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Re: Wet exhaust- which metal?

On my Yanmar the mounting plate and the threaded exhaust elbow are joined by a LEFT-HAND thread. I discovered this only by accident when the parts dealer told me. What a difference when I put the old elbow in a vise to remove the mounting plate. I went through all the gyrations that you did. I think manufacturers do this to guarantee that you can't use less expensive steel plumbing fittings.

You can't use brass because it's an alloy of zinc and copper. The hot seawater sucks the zinc out in a relatively short time and you are left with a pinkish, almost all porous copper elbow.

The biggest problem to using materials other than your model's replacement elbow is that pesky exhaust flange. It's perfectly good when you eventually spin off the elbow portion, and the manufacturer's elbow already has the seawater exhaust tube in the right place.
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Old 06-04-2015, 08:04   #4
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Re: Wet exhaust- which metal?

Try this link for all SS

Yanmar Stainless Steel Exhaust Mixing Elbow GM Diesel Models 128370 13600 | eBay
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Old 06-04-2015, 10:08   #5
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Re: Wet exhaust- which metal?

Don't use any copper alloys with diesel. Even with most diesel fuel being low sulfur, copper and sulfur is a bad combination. The copper will corrode.
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Old 06-04-2015, 10:13   #6
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Re: Wet exhaust- which metal?

Quote:
Originally Posted by swoop12 View Post
Hi. I have a westerbeke w13 which cracked the wet exhaust elbow. I have since bought a new one and am having a lot of fun trying to get the old elbows and couplers (nipples) apart. My question is what metals are acceptable to make this out of? Currently the elbows are 304 stainless steel and do not look corroded. The couplers I do not think are stainless as they are quite rusted and seized to the elbows and manifold exhaust flange (penetrating oil, heat gun, bench vice, and a large wrench) . At the hardware store all I could find in the 1.5 npt inch size are galvanized steel. I don't want to use this. At west marine I can find brass (yellow) couplers and elbows. They are expensive but available. I have no idea where to look for stainless elbow and couplers/nipples. Anyone have a reason why I can't use brass other than cost?

If I should use stainless steel any idea where I can get the parts ? Also what about using brass nipples with stainless elbows? Will those metals seize together?

Thanks

The coupler nut on Yanmars set up is left hand threaded on one side, the other side is standard right hand thread,the reason is to facilitate a removal of the mixing elbow in place, not removing it from the exhaust flange.
This never actually happens because of corrosion.

But we're not speaking Yanmar here.
Bronze fittings are marine grade, don't use brass.
And anti seize compound on the threads will help in disassembly later.


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Old 06-04-2015, 10:14   #7
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Re: Wet exhaust- which metal?

Regardless of what you use, ALL metals should be the same (if you are in salt water, raw water cooling).

DIS-similar metals in salt water (less so for fresh water) will generate a (small) electric current where they are in contact and corrode like crazy.

I had the same issue on my trimaran - aluminum touching cast iron touching stainless - joints were impossible for me to disconnect (fortunately when things failed I was near a large marina with a hydraulic press - they took it apart for me)
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Old 06-04-2015, 10:23   #8
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Re: Wet exhaust- which metal?

For SS look on McMaster Carr. They might have it. On a small diesel the original SS went bad pretty fast, I put galvanized pipe fittings on and it lasted longer than the SS did. However, that was many years ago and the Galvanizing looked quite different back then then it does now.
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Old 06-04-2015, 10:29   #9
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Re: Wet exhaust- which metal?

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Don't use any copper alloys with diesel. Even with most diesel fuel being low sulfur, copper and sulfur is a bad combination. The copper will corrode.

I've got 8 long copper lines carrying diesel to and from the engines. they've been doing it since 1975 with nary a leak, soft spot or any other problem.
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Old 06-04-2015, 10:31   #10
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Re: Wet exhaust- which metal?

I don't think my flange is left hand thread, but I will double check next time I am there.

Yes the dissimilar metals galvanic corrosion issue is what I think I am dealing with. At least it seems the elbows in the system are stainless and the couplers are galvanic. The mixing elbow I got as a replacement from Westerbeke; I think it might even be aluminum. Truthfully i'm not super good at telling metals apart especially if painted/rusted. Unless they have 304 stamped on them.

http://www.westerbeke.com/Store/13-2...f73a201c69e020

If you look at this schematic my problem is that part 17 is stuck in 11. I am not even sure if part 11 is stainless. I would think.... Then due to my particular boats set up there are two more couplers and elbows that reach over to the mixing elbow then out the back. I am only trying to get part 11 free and then use new ss or bronze I suppose as long as I can find them.

I will definitely be using antiseize on these threads if I ever get them apart.

I guess the hunt is on for some 1.5 inch stainless steel elbows and couplers/nipples.
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Old 06-04-2015, 10:36   #11
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Re: Wet exhaust- which metal?

http://www.westerbeke.com/Store/13-2...f73a201c69e020

If you look on this diagram part 17 is seized to 11. I am not even sure if 11 if stainless or not. and given the rust I definitely dont think 17 is stainless. I don't think it is left handed thread, but I will double check.

On my particular boat there are two more couplers and elbows to get the mixing elbow which I bought from Westerbeke.

Sounds like brass is not a good choice. I will have to look for the new couplers and elbows in stainless steel. or bronze as a back up. I definitely plan on using antiseize.
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Old 06-04-2015, 10:43   #12
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Re: Wet exhaust- which metal?

I am a retired food process engineer. We use AL-6XN in processing applications with corrosive/oxidative chemicals. It is a super alloy of stainless steel. It is available in sch 10, 40 and 80. Expensive - but it will last your lifetime plus that of your kids.
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Old 06-04-2015, 12:03   #13
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Re: Wet exhaust- which metal?

Quote:
Originally Posted by swoop12 View Post
Hi. I have a westerbeke w13 which cracked the wet exhaust elbow. I have since bought a new one and am having a lot of fun trying to get the old elbows and couplers (nipples) apart. My question is what metals are acceptable to make this out of? Currently the elbows are 304 stainless steel and do not look corroded. The couplers I do not think are stainless as they are quite rusted and seized to the elbows and manifold exhaust flange (penetrating oil, heat gun, bench vice, and a large wrench) . At the hardware store all I could find in the 1.5 npt inch size are galvanized steel. I don't want to use this. At west marine I can find brass (yellow) couplers and elbows. They are expensive but available. I have no idea where to look for stainless elbow and couplers/nipples. Anyone have a reason why I can't use brass other than cost?
If I should use stainless steel any idea where I can get the parts ? Also what about using brass nipples with stainless elbows? Will those metals seize together?
Thanks
Assuming you are turning the right way, you need a bigger vise and bigger wrench, more heat...

Replace with black iron rather than galvanized.
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Old 06-04-2015, 12:03   #14
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Re: Wet exhaust- which metal?

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Originally Posted by lady sophie View Post
I am a retired food process engineer. We use AL-6XN in processing applications with corrosive/oxidative chemicals. It is a super alloy of stainless steel. It is available in sch 10, 40 and 80. Expensive - but it will last your lifetime plus that of your kids.
The trick with AL-6XN, or *ANY* of the super austinetic SS's or duplex SS's is finding someone who can weld it correctly. They require different techniques and fillers. Most "marine" fabricators will give you a blank stare. Something to keep in mind if you plan to cruise remote areas and find you need repairs to your unobtainium widgit.
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Old 06-04-2015, 13:40   #15
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Re: Wet exhaust- which metal?

300 series Stainless can work harden and crack if exposed to vibration especially in the corrosive environment of an exhaust. Think I'd stick with galvanized or un galvanized Iron pipe for cost and reliability. It will eventually corrode through but life span in measured in decades in most applications.

Getting Yanmar exhausts apart is a real bitch. Had to call in a mechanic to disassemble mine because it needed a humongous vise strong enough to clamp it in place so he could unscrew the pieces with an equally humongous pipe wrench and heating to a cherry red with an acetylene torch.
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