Yanmar exhaust elbows

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Medway Matt

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A couple of years ago there was a fair bit of discussion on this forum regarding replacement Yanmar exhaust elbows, particularly pattern parts made in stainless available from ExhaustElbow.com and how well made thy appear to be. What I haven't been able to find is much in the way of comment regarding how durable they are. Does anyone know?

As I'm sure you've already worked out, we have our elbow off and it's got quite a deep pit about half way along the inner tube and a suspicious swelling on the inner tube adjacent to the water feed point, although as I haven't a good probe at this bit yet I'm not sure how serious it is. The welding at the flange looks ok but I haven't had a good dig at that either yet. While the elbow may well be ok for a while yet, our feeling is that we'd rather replace the elbow than risk having to replace the cylinder head.

Cheers
Matt
 
Several years ago I bought 3 exhaust bends of him. I asked people who I knew had 1GM10 engines if they also needed one to keep the postage down.
We have had no problems with them and they were very well made, the original Yanmar elbows are also stainless but are not polished.
Mine was still okay when I sold the boat a few years later and I think the other 2 are still in use.
 
I bought one for myself and another for a pal (to keep postage down) for 4JH4's. Ended up having to pay customs tax of about £150 taking away much of saving. If I had bought just one it may have slipped through being nearer the duty threshold.
They were well made and fitted perfectly, been on 3 years now and looking OK. The Yanmar original had lasted 10 years, heavy pitting and slight leak but keeping as a spare.
I needed to replace the studs due to corrosion.
 
E-mac said:
I bought one for myself and another for a pal (to keep postage down) for 4JH4's. Ended up having to pay customs tax of about £150 taking away much of saving. If I had bought just one it may have slipped through being nearer the duty threshold.
They were well made and fitted perfectly, been on 3 years now and looking OK. The Yanmar original had lasted 10 years, heavy pitting and slight leak but keeping as a spare.
I needed to replace the studs due to corrosion.
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They are fine on non turbo engines, but beware of the fact that on a turbo engine they can set up galvanic corrosion of the aluminium alloy turbo casing. I know because a stainless elbow on my engine did just that and I had to replace it with a genuine Yanmar cast iron elbow in order to save the turbo from further damage. The corrosion damage to my turbo was internal, and came close to scrapping it.
 
Norman_E said:
They are fine on non turbo engines, but beware of the fact that on a turbo engine they can set up galvanic corrosion of the aluminium alloy turbo casing. I know because a stainless elbow on my engine did just that and I had to replace it with a genuine Yanmar cast iron elbow in order to save the turbo from further damage. The corrosion damage to my turbo was internal, and came close to scrapping it.
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I don't think I understand that. Where is the water needed for corrosion?
 
This thread has prompted me to do a quick search for one for my D1-20, as I feel that replacement of the original will be required soon. I found that there is a selection of s/s ones available closer to home, with no import duties payable (notwithstanding Brexit :( ). The average price seems to be a in or about €250.
 
I spotted quite a few complaints back in 2009-2010 about the elbows on my 4JH4AE Yanmar. I saw enough reports to persuade me to buy a spare from Yanmar (reasonable discount but still expensive). I was planning to leave UK on an extended cruise for about 10 years and wanted a few spare items. I also painted the almost new elbow with a protective coating. I had used the paint on my old BUKH elbow for about 20 years and it seemed to work. I can't remember what it was but seem to remember something about interlocking fibreglass strands and high-temp resistance. I wish I could remember the type of paint I used.

Sod's law meant that I later discovered it had only affected a single batch of elbows (at least that's what Yanmar claimed) and mine should be OK.

Having a spare lying around means the existing one still looks fine. I take it off at the end of every season and it still seems fine after 11 years use.
 
Medway Matt said:
A couple of years ago there was a fair bit of discussion on this forum regarding replacement Yanmar exhaust elbows, particularly pattern parts made in stainless available from ExhaustElbow.com and how well made thy appear to be. What I haven't been able to find is much in the way of comment regarding how durable they are. Does anyone know?

As I'm sure you've already worked out, we have our elbow off and it's got quite a deep pit about half way along the inner tube and a suspicious swelling on the inner tube adjacent to the water feed point, although as I haven't a good probe at this bit yet I'm not sure how serious it is. The welding at the flange looks ok but I haven't had a good dig at that either yet. While the elbow may well be ok for a while yet, our feeling is that we'd rather replace the elbow than risk having to replace the cylinder head.

Cheers
Matt
Click to expand...
I bought the parts to fabricate a stainless one for my 3GM 20 and got it welded locally. Its been on for 4 years now and working perfectly.
If you want details pm me.
 
Thanks all.

I'll be attacking the build up on the inside of our current elbow tomorrow to get a better idea of it's condition but suspect I'll be getting a replacement to be on the safe side.
The engine's twenty years old and runs beautifully with about 1000 hours service - we use the boat a lot but the engine not so much, I assume the PO was the same.
 
vyv_cox said:
I don't think I understand that. Where is the water needed for corrosion?
Click to expand...
I asked the same question, but the damage inside the aluminium turbo housing was plain to see, and the face where the elbow bolted on to the turbo had to be carefully filed flat by rubbing on a sheet of emery cloth laid on a flat board.
 
Am in process of servicing mine (D2 Penta); what do folks think of the concern about stainless steel and temperature variation? In case I decide to replace...
 
RJJ said:
Am in process of servicing mine (D2 Penta); what do folks think of the concern about stainless steel and temperature variation? In case I decide to replace...
Click to expand...
Not sure what you mean by that. 300 series stainless steels are austenitic, which means their microstructure remains unchanged until they melt. Which is why 300 series cannot be strengthened by heat treatment.
 
I heard a rumour this was the reason the engine builders didn't go for stainless (prone to stress cracking induced by expansion/contraction) and we should stick to their parts when we replace. So your recommendation seems to be a tick for stainless? Thanks. I know little but want to make the right choices like all of us!
 
RJJ said:
I heard a rumour this was the reason the engine builders didn't go for stainless (prone to stress cracking induced by expansion/contraction) and we should stick to their parts when we replace. So your recommendation seems to be a tick for stainless? Thanks. I know little but want to make the right choices like all of us!
Click to expand...
The yanmar elbow on my 3GM30 F failed in the way you describe, by fatigue, not stress cracking. The case history is on my website. It is a design problem, not materials. Would happen in mild steel just the same.

As a high stress, low cycle form of fatigue I think it is associated with the number of starts. Mine failed at around 2000 hours, probably about the number of starts.
 
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