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Old 06-08-2012, 08:18   #1
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Yanmar 2GM20F Exhaust Mixer/Elbow

I, like I think most Yanmar owners, go through exhaust mixers at an alarming pace.

On the 2 engines, in 5 years, I have bought 6 elbows. Some replaced by Yanmar under warranty, but most not. They always leak in the same place, the weld, and sometimes inside which caused my heat exchanger body to rot out also as I did not know what to check in the early years on my boat. Often as few as 50 hours and I will start to see the signs of the unit failing.

Last time I complained to Yanmar about it, they told me they had no other warranty claims or customer complaints about this elbow. A bit unbelievable to me.

They cost about $160 each for the Yanmar elbows, which adds up over 5 years, for a part that I would hope would last 5 years....

So, looking for alternatives.

Seems like Stainless people are a bit wary of, but that seems to be what the aftermarket elbows are made from. Are there certain questions/criteria I should use when looking for someone to fabricate new ones for me?

If not stainless, what? I cannot use a typical U shaped unit as I have very little clearance above the engine so I cannot really go "up" then down. Pretty much has to be similar shape to what I have now.

Any thoughts/experiences would be great.

I lean towards getting a SS one made, but 304, 316? I see SS with "L" after it. Anything special for the welds that needs to be done. Is TIG welding OK for it?

Thanks!
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Old 06-08-2012, 08:22   #2
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

I have a genny with a 304, TIG welded manifold (home made)..... with 5000+ hours. I've made others for larger engines with similar results.
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Old 06-08-2012, 08:31   #3
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

I would be looking for some other cause besides looking for a different material.

Both the Yanmars I've owned had/have their orginal elbows at 1700hrs/22 years and 750 hrs/11 years.
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Old 06-08-2012, 08:38   #4
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Quote:
Originally Posted by Don Lucas View Post
I would be looking for some other cause besides looking for a different material.

Both the Yanmars I've owned had/have their orginal elbows at 1700hrs/22 years and 750 hrs/11 years.
Unfortunately I have looked for other causes extensively, and still have the same issues.

I have made sure there is no pressure on the elbow from the exhaust hose. Not really sure what else could cause the failures. Both have very straigt runs of exhaust hose, and happens on both engines. Have talked to Yanmar, sent photos, had mechanics look, all say the same thing, crappy elbows (well, Yanmar officials did not say this, but authorized dealers have).

If you have other thoughts on what would cause it, I am happy to attack the problem another way, but am doubtful.
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Old 06-08-2012, 09:10   #5
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

I would be thinking about heating and cooling down, especially the cooling down based on cracking the welds. Do you allow the engines to warm up prior to use normally? Do you allow the engines to run at idle/low speed speed after use so the elbows cool-down slower and have less heat stress?

Are the elbows heat wrapped or just bare exposed to the air?
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Old 06-08-2012, 09:11   #6
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Quote:
Originally Posted by kiltym View Post
Unfortunately I have looked for other causes extensively, and still have the same issues.

I have made sure there is no pressure on the elbow from the exhaust hose. Not really sure what else could cause the failures. Both have very straigt runs of exhaust hose, and happens on both engines. Have talked to Yanmar, sent photos, had mechanics look, all say the same thing, crappy elbows (well, Yanmar officials did not say this, but authorized dealers have).

If you have other thoughts on what would cause it, I am happy to attack the problem another way, but am doubtful.
Interesting, (2) 3GM30s, 9+ years old, 1800 hours, original elbows, no leaks. Mine look like stainless. I took one off a few years back to check for buildup and it was clean.

Do your zincs disappear quickly?
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Old 06-08-2012, 09:21   #7
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Quote:
Originally Posted by Don Lucas View Post
I would be thinking about heating and cooling down, especially the cooling down based on cracking the welds. Do you allow the engines to warm up prior to use normally? Do you allow the engines to run at idle/low speed speed after use so the elbows cool-down slower and have less heat stress?

Are the elbows heat wrapped or just bare exposed to the air?
Yes, engines are always warmed up for about 3 minutes at 1200rpm before engaging transmission. Engines are then used at relatively low RPM for the next 10 minutes or so while we pull in our anchor. We always let engines cool, based on how long we have been running at high rpms, but running at idle for a period of time, 5 minutes or so, before shutting off. We live on anchor, so usually the engines are pretty cool by the time the anchoring is done anyway.

Elbows are just exposed to air, just as the photo shows. Nothing else.
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Old 06-08-2012, 09:27   #8
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Quote:
Originally Posted by DotDun View Post
Interesting, (2) 3GM30s, 9+ years old, 1800 hours, original elbows, no leaks. Mine look like stainless. I took one off a few years back to check for buildup and it was clean.

Do your zincs disappear quickly?
No zincs on 2GM20F. Only on the saildrives.

The insides of them are clean (since I have to change them every year ). Only when I first bought the boat was there a little buildup inside the elbows, but now they are basically clean, and I remove and check once per year if the elbow was not replaced.

They leak at the weld shown in the photo, and the one time that got real bad, also at the weld on the surface of the mounting flange which caused the heat exchanged to rot out. Since then, I don't let them get bad, and replace once I see a small amount of weeping occur.
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Old 06-08-2012, 09:31   #9
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Here are some photos of the installations, in case anything looks "odd" to anyone.
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Old 06-08-2012, 09:35   #10
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Quote:
Originally Posted by kiltym View Post
Yes, engines are always warmed up for about 3 minutes at 1200rpm before engaging transmission. Engines are then used at relatively low RPM for the next 10 minutes or so while we pull in our anchor. We always let engines cool, based on how long we have been running at high rpms, but running at idle for a period of time, 5 minutes or so, before shutting off. We live on anchor, so usually the engines are pretty cool by the time the anchoring is done anyway.

Elbows are just exposed to air, just as the photo shows. Nothing else.
Your warm up and cool down sound good to me. But there isn't really any doubt to me that this is a heat stress issue at the weld.

Welds are always more likely to crack than other sections due to the heat stress of the process. If it hadn't been that you have gone though so many of the elbows I would wonder about whether they were getting a good gas blanket during the welding to keep oxygen out of the weld when they did that elbow.

You might try wrapping the elbows with a heat shield. This will allow the the welds to cooldown mush slower to equalize the stress.

May be do nothing, but worth a try I would think.
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Old 06-08-2012, 09:46   #11
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Quote:
Originally Posted by Don Lucas View Post
Your warm up and cool down sound good to me. But there isn't really any doubt to me that this is a heat stress issue at the weld.

Welds are always more likely to crack than other sections due to the heat stress of the process. If it hadn't been that you have gone though so many of the elbows I would wonder about whether they were getting a good gas blanket during the welding to keep oxygen out of the weld when they did that elbow.

You might try wrapping the elbows with a heat shield. This will allow the the welds to cooldown mush slower to equalize the stress.

May be do nothing, but worth a try I would think.
I can try this, not a big deal to try.

The current elbows are starting to show signs again so I need to bring spares with me back to Panama in 2 weeks.

Should I get ones made out of SS from a after market, or just buy 2 more Yanmar elbows again, that is the question......
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Old 06-08-2012, 09:51   #12
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

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Originally Posted by kiltym View Post
I can try this, not a big deal to try.

The current elbows are starting to show signs again so I need to bring spares with me back to Panama in 2 weeks.

Should I get ones made out of SS from a after market, or just buy 2 more Yanmar elbows again, that is the question......
Well wouldn't continuing to do the same thing you have been doing be a sign of insanity?
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Old 06-08-2012, 09:59   #13
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

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Well wouldn't continuing to do the same thing you have been doing be a sign of insanity?
I would certainly think so, yes .

So, back to the original question about what I need to look for in a SS mixer/elbow......
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Old 06-08-2012, 10:20   #14
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

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Originally Posted by kiltym View Post
So, back to the original question about what I need to look for in a SS mixer/elbow......

I don't have any first hand knowledge. But have read numerous threads and personal blog sites over the years where they changed to a SS elbow with good results. I would definitely be looking for the shop to be well experinced in SS welding.
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Old 06-08-2012, 17:23   #15
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Re: Yanmar 2GM20F Exhaust Mixer/Elbow

Are just the welds failing? Take 'em to a welding shop, they can fix 'em.
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