yanmar exhaust elbow. beware!

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Spyro

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I know its been talked about a lot but I thought I'd share some pics. My elbow looked perfect from outside but as I've had the boat 5 years and never had it off I thought I'd check it over. From the fist pic you can see it looked fine. When I removed it I was surprised to see the inside fall out without any poking or proding. It does really look like poor manufacturing.

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Been there before our 3gm30 had the same problem when we bought the boat. I now remove the elbow at least once each year, normally before holidays just to make a visual check and pour boiling water down the outer tube to see if the joint weeps.
 
thanks for posting

i take the exhaust off about once a year, can get a good look in with a mirror and put my finger in etc

wonder if i should be taking this fitting off and pressure testing the inner bit somehow?
 
CET1 said:
Been there before our 3gm30 had the same problem when we bought the boat. I now remove the elbow at least once each year, normally before holidays just to make a visual check and pour boiling water down the outer tube to see if the joint weeps.
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Ditto for our 4JH4AE. I cleaned and painted the inside when virtually new and it still seems in good condition with no pin holes. Can't remember the type of paint, think it has glassfibre in an epoxy and it bonded to the metal quite well.

I also keep spare elbow as it will still fall apart eventually.
 
RichardS said:
Would it still work without the inner core?

Richard
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I suspect that it would, at least for a while. Photo shows the manifold on our little motorsailer. I have not removed it but I doubt if there is space internally for a bend and second tube.
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I guess that the failure is due to corrosion at the weld, although fatigue is a possibility. Impossible to say without a proper examination.
 
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Yes quite common, its something to do with the exhaust gasses when mixed with salt water eating at the welds of the elbow. What will eventually happen is water will find its way into the cylinder through an open exhaust valve, then when you start the engine you will end up bending a con-rod.
 
Once the inner tube has broken free, the water that is injected can flow back into the exhaust manifold with the potential to cause major damage to the engine. A thorough check each year is highly advisable.
 
black mercury said:
What will eventually happen is water will find its way into the cylinder through an open exhaust valve, then when you start the engine you will end up bending a con-rod.
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stuey_two said:
Once the inner tube has broken free, the water that is injected can flow back into the exhaust manifold with the potential to cause major damage to the engine. A thorough check each year is highly advisable.
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But I guess that's the beauty of Vyv's design - the water won't flow uphill. Unfortunately my Yanmar is not like Vyv's so the caution is welcome.

Richard
 
This thread is very timely, I was debating resurrecting an old thread on exactly the same subject :)

I was planning to have my 2GM20F elbow off in a fortnight or so and check it. Just in case it's U/S I have been in touch with Ben at Exhaustelbows.com and the ones he sells are apparently suitable for the F model. However, his website says they are made from 304 stainless.

Thoughts from anyone? Particularly anyone who has fitted one from Ben etc...
 
I have a spare brand new stainless one for sale for a 1GM10. Also my old one is still perfectly serviceable for a lower price.
 
KevO said:
Thoughts from anyone? Particularly anyone who has fitted one from Ben etc...
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I have one of his ... it has been on since I replaced the head three years ago. I plan to take it off this spring and have a hard stare at the inside, but externally it has been fine so far, and at a third of cost of a Yanmar one. My only concern was with the water injection spigot, which is parallel sided. I would have preferred a raised ring round the end, as on the OEM one, but the hose has stayed put so it doesn't seem to be an issue in practice.
 
JumbleDuck said:
I have one of his ... it has been on since I replaced the head three years ago. I plan to take it off this spring and have a hard stare at the inside, but externally it has been fine so far, and at a third of cost of a Yanmar one. My only concern was with the water injection spigot, which is parallel sided. I would have preferred a raised ring round the end, as on the OEM one, but the hose has stayed put so it doesn't seem to be an issue in practice.
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I saw a picture of one of those with the parallel sides, couldn't understand why it would be like that when the hose is round.
 
Yeah, mine looks perfect on the outside too. I have no idea how long since it was fitted so I'll have it off and check inside. I want to have a plan in case it's knackered but I don't want to "buy cheap, buy twice", I want something that will last even though I'll inspect it annually from now on.
 
KevO said:
This thread is very timely, I was debating resurrecting an old thread on exactly the same subject :)

I was planning to have my 2GM20F elbow off in a fortnight or so and check it. Just in case it's U/S I have been in touch with Ben at Exhaustelbows.com and the ones he sells are apparently suitable for the F model. However, his website says they are made from 304 stainless.

Thoughts from anyone? Particularly anyone who has fitted one from Ben etc...
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If the failed one shown in the OP photograph is the result of sensitisation, i.e. weld corrosion, then its cause is using either 304 or 316 as opposed to 304L or 316L. These two are the low carbon version, preferable for welding where corrosive conditions will be involved.
 
Two things occur to me;

1) this is a problem that is so, so common to Yanmar engines (my 1GM10 had it and now my 3YM20) that I cannot understand why Yanmar don't fix or redesign it? The designs are 20 years or so old or more and they STILL have not sorted it. How many engines have been damaged or even ruined by this awful piece of junk?

2) The warnings to check the exhaust are nowhere near visible enough. Apparently my local Yanmar dealer suggests EVERY year but where does it tell the luckless owner to do this? Certainly not the boat builder and I haven't found it in the user manual - happy to be corrected if it is there, but if it is, why not highlighted as it is a huge potential safety problem if your engine breaks at a crucial moment.
 
vyv_cox said:
If the failed one shown in the OP photograph is the result of sensitisation, i.e. weld corrosion, then its cause is using either 304 or 316 as opposed to 304L or 316L. These two are the low carbon version, preferable for welding where corrosive conditions will be involved.
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Ben says they are currently 304 with 308L welds. He has been directed to these threads and says he will consider changing to 304L for future products :)
 
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