marcuc
New Member
Was wondering if anyone has tried to put a corrosion proof coating on the inside of the water jacket of a new exhaust elbow say on a yanmar 3ym30 or other? Would love to avoid the mess the raw water spray makes when the weld fail
Coating a new exhaust elbow inside to slow corrosion?
- Thread starter marcuc
- Start date
Refueler
Well-Known Member
I must admit the thought is intriguing ... based that I am about to remove elbow from my VP AQ170 which has a big hole in it !!
oldgit
Well-Known Member
you can get stainless replacement risers for some diesel VP engines
alahol2
Well-Known Member
I reckon BBQ paint could be worth a try.
Refueler
Well-Known Member
Its a Gasoline AQ170 ... but I have a Metals guy ready to repair it once its removed from the boat.
A new cast one is over 400 quid ... some places want 700 !! Stainless ?? I shudder to think what price for that !!
My guy will repair for about 20 quid ... just need to find the midget who can get to back of engine to remove it !!
We did consider GunGum paste and then wrap with bandage ... but again its access to it .. and the metal is crumbling around the hole .. so needs cutting back and then patch inserted ... welded etc.
PabloPicasso
Well-Known Member
Hmmm, Replacing with new would be the better course of action. IF you can find one A STAINLESS version would be ideal. A quick google https://www.marineengine.com/boat-f...ifold-for-volvo-penta-aq165-and-aq170.451379/
Or see pic attached for another option
Think of the hassle of having to crawl into that tiny space again, especially if a stud is corroded, won't move, or snaps
400quid will seem like money well spent then....
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Refueler
Well-Known Member
Hi Pablo ...
The guy who will repair - is a Master at his trade .. and has already made clear that he will renovate the item fully.
He's repaired gear for me a number of times and believe me - better than original ....
The guy who will repair - is a Master at his trade .. and has already made clear that he will renovate the item fully.
He's repaired gear for me a number of times and believe me - better than original ....
marcuc
New Member
I found it a frustrating job trying to get a non porous weld on salt impregnated steel no matter how much I cleaned and ground it back after many runs it wasn't water tight so I got a new one but haven't bolted it on yet. I've got a ceramic exhaust paint now which I'm going to try and coat the inside of the water jacket
Thanks for the fatigue page notes that could definitely be the case for the outside tube but after cutting apart I found the inside jacket tube was corroded all over as well and it's really only carrying the load of hot exhaust on one side and salt water on the other
ducked
Well-Known Member
I used to routinely rust treat non-cat exhausts by putting some beercan and a teaspoon of Portland cement insiden the mainifold. Aluminium flame sprays the inside, cement neutralises acids. In theory.
These of course weren't salt water cooled. Those are going to be sacrificial, fairly inevitably.
These of course weren't salt water cooled. Those are going to be sacrificial, fairly inevitably.
Neeves
Well-Known Member
I'm not sure what all the fuss is about. I believe a UK distributor sells cast stainless exhaust identical to this one
Neuer Auspuffkrümmer aus Edelstahl 304, für Volvo Penta MD2010 MD2020 MD2030 21190094 ï¼ 861906 - AliExpress 34
It may not be identical but they use the same picture as Aliexpress. Its not particularly expensive.
Someone will be able to advise who the imported is - or you can buy direct from Aliexpress. I did a search 'Parts4engines'
There have been a number of threads:
Stainless Steel Exhaust Elbow- 304 or 316?
Now - whether its any good I cannot comment. I did buy and use one but sold the boat before I had had time to evaluate.
Jonathan
Neuer Auspuffkrümmer aus Edelstahl 304, für Volvo Penta MD2010 MD2020 MD2030 21190094 ï¼ 861906 - AliExpress 34
It may not be identical but they use the same picture as Aliexpress. Its not particularly expensive.
Someone will be able to advise who the imported is - or you can buy direct from Aliexpress. I did a search 'Parts4engines'
There have been a number of threads:
Stainless Steel Exhaust Elbow- 304 or 316?
Now - whether its any good I cannot comment. I did buy and use one but sold the boat before I had had time to evaluate.
Jonathan
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ducked
Well-Known Member
I have a .pdf copied from a thread, I think on here, where someone made one up from standard pipe fittings. Looked like it should have worked and, at least in Taiwan, I think I would have been able to find the fittings. In The Yook I'm not so sure.
Quick look I couldn't find the source but I'll have another look later
Edit: Cant find source, so if file uploads ok, apologies to the author for lack of attribution
Quick look I couldn't find the source but I'll have another look later
Edit: Cant find source, so if file uploads ok, apologies to the author for lack of attribution
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vyv_cox
Well-Known Member
Your post asked for answers to cracking of the outer tube. Nothing to do with corrosion of the inner. I believe that cracking is low cycle, high stress fatigue almost certainly related to the number of stop/start cycles, i.e. nothing to do with corrosion. In most cases I suspect that cracking will occur well before corrosion becomes a major problem.
Tranona
Well-Known Member
The OP has a Yanmar which is a completely different design. It is already made of stainless and it is the weld of the inner to the outer tubes that has failed. Volvo is a casting (iron in the original) which usually fails due to corrosion.
marcuc
New Member
Answer is buy or build a new one as needed thanks for the inputs
Refueler
Well-Known Member
Well aware of that .... I have Perkins ... Yanmar and Volvo engines ....
Go back to my first reply on this thread and you will see I was relating - not to the brand of engine - but to the idea of coating the internal ....
Neeves
Well-Known Member
I was aware the OP had a Yanmar but though jogging his enthusiasm might allow him to search the forum threads, of which there are many, and/or look at website of the UK distributor. It seems logical that a distributor for Volvo parts might also stock Yanmer parts.
Jonathan
Neeves
Well-Known Member
Maybe I have been unlucky but.....
On my Volvo cast steel exhaust elbows the major failure mechanism has been the development of a carbon impregnated calcium deposit that fills and eventually blocks the elbow until an approx 5mm hole is left and the clogged elbow restricts exhaust gas flow. This deposit can be removed by soaking in concentrated acid, which underlines its a calcium rather than carbon deposit. Using acid to clean the blockage, I found, can clean (at least in part) the deposit twice, but I suspect also damages the steel and if you are optimistic and try a third time the elbow develops a significant hole through the wall (of the elbow). Using concentrated acid seems effective but you do need to plan how you are going to dispose of the spent acid (and conc acid is nasty - take extreme care).
If the mechanism causing the deposit could be confidently identified and a sensible remedy or practice proven then elbow life, in my case, would be significantly improved. Whether the cast stainless elbows, Aliexpress, parts4engines, offer any improvement in life - I don't know - but the Aliexpress models are cheaper than genuine Volvo cast steel elbows, in Australia, (though you need to wait till the part arrives from China - so you need to be patient or plan ahead).
The stainless elbow I received from Aliexpress was supplied with a new gasket - looked the part and fitted correctly (but as I said I sold the boat before the elbow had time to prove itself).
Jonathan
On my Volvo cast steel exhaust elbows the major failure mechanism has been the development of a carbon impregnated calcium deposit that fills and eventually blocks the elbow until an approx 5mm hole is left and the clogged elbow restricts exhaust gas flow. This deposit can be removed by soaking in concentrated acid, which underlines its a calcium rather than carbon deposit. Using acid to clean the blockage, I found, can clean (at least in part) the deposit twice, but I suspect also damages the steel and if you are optimistic and try a third time the elbow develops a significant hole through the wall (of the elbow). Using concentrated acid seems effective but you do need to plan how you are going to dispose of the spent acid (and conc acid is nasty - take extreme care).
If the mechanism causing the deposit could be confidently identified and a sensible remedy or practice proven then elbow life, in my case, would be significantly improved. Whether the cast stainless elbows, Aliexpress, parts4engines, offer any improvement in life - I don't know - but the Aliexpress models are cheaper than genuine Volvo cast steel elbows, in Australia, (though you need to wait till the part arrives from China - so you need to be patient or plan ahead).
The stainless elbow I received from Aliexpress was supplied with a new gasket - looked the part and fitted correctly (but as I said I sold the boat before the elbow had time to prove itself).
Jonathan
vyv_cox
Well-Known Member
From what I understand, never having owned a. Volvo engine, this is a common failure mode for these elbows. Bukh elbows mostly seem to corrode away and, as in my previous post, Yanmar ones fail in fatigue. Interesting that design variations in such a simple device can generate such widely differing failure modes.
alahol2
Well-Known Member
Is there any reason why many exhaust elbows are complex, dual walled (thus expensive) affairs whereas Beta elbows are just a bent pipe with an injection point?