Stainless Steel Exhaust Elbow- 304 or 316?

[Neeves]

None of this answers a question - is a 304 cast elbow better than a cast iron (or steel) cast elbow? (Yes - 316 might be a better option, or not, than 304 - but 316 is not on offer). I do find it interesting that the chosen product IS 304 NOT 316 and as the difference in cost is not greatI my conclude they think 304 is better.

Elbows, cast steel or iron, do not fail because of the environment - they fail because they block. There is corrosion in the cast iron/steel elbows but it is minor as they block more quickly than corrode. I don't think anyone suggests the environment is not aggressive but other than blocking the cast ones seem to withstand the rigours.

Noting the few comments from people who have actually used a stainless elbow, commonly fabricated, the conclusion looks positive - but it is hardly statistically sound. When I consider use 'Fe' metals in industrial pipework I note that in many, or most, occasions stainless is chosen in preference to iron or steel - (though often stainless is chosen for reasons other than their lack of corrosion).

The most frustrating part of such debates is that it will take a considerable length of time to come to a conclusion.

Tranona beat me to it with a much more erudite response.

To me the fact that the Aliexpress elbow is cheaper, than a cast steel version, is not critical -I'd pay extra for longevity. But if its both less expensive and has a better performance - no brainer. I know buying from Aliexpress neither supports a local chandler nor is very convenient - but if the cast 304 version is 'better' some local entrepreneur will import them and add them to their already extensive list of Chinese components, If Ronstan can have their LFRs made in China I don't feel so bad about buying one elbow, potentially 2 elbows.

Jonathan

 

[Neeves]

Bit of both. The first one I had fail was about 7 years old and I believe was brazed - was not there when it was done by my mechanic in Greece. The latest one failed after 3 years and was replaced in the belief that it was covered by the 5 year warranty. However Volvo rejected the claim as it only covered the engine and transmission. I had the old one repaired by welding a plate over the external face around the spigot. Gave it to the new owner as a present. Would be good if Volvo supplied the aft end plate as a spare.

The problem is easy to see. The outlet spigot comes through the plate at an extreme angle and the inaccessible lower section of the weld is under seawater most of the time, usually cold and stagnant. Perfect conditions for crevice corrosion.

Yes, you can use the Vetus WLOCKR 45 which is slightly longer and higher so needs a bit of tweaking of the hose and a different attachment to the panel . Roughly half the price of the Volvo one and potentially far more durable.

Thanks Tranona - I'll be looking at the Vetus version - once I've sorted out the elbow and have the engine running again.

Jonathan

 

[bitbaltic]

Following this with interest as I’ve just changed the elbow on my MD2020 from the original cast iron to a cast stainless. Unfortunately I didn’t do it myself (that’s a job for the marine engineers) and I’m surprised to see that the part can’t be a penta original (as I supposed) because all the stainless elbows seem to be third party and not OEM things. You learn a lot in the forum.

putting it in context though, the original elbow was 20 years old and as far as I know there was nothing wrong with it (performance wise) other than moderate surface rust. I changed it as part of a deliberate preventative maintenance programme as the boat hit 20 years old this past winter. Thinking being, if the previous iron elbow was good for 20 years then it’s time to bank that and grab another 20 years without worrying about it. General opinion seems to be that any new elbow (iron or stainless) is as good as the original so I reckon I’m happy with that.
I might enquire about what manufacturer’s part it actually is though as it seems from this thread that it can’t be a Volvo OEM one.

 

[Zing]

It’s not good enough. 304 is junk, 316 is better junk. Buy 2205 or 2207 or better stainless grades. There are some very impressive grades if you take the time to research it. The intrinsic cost is often less, but life should be massively better. Consider also titanium grade 5.

 

[Daverw]

It’s not good enough. 304 is junk, 316 is better junk. Buy 2205 or 2207 or better stainless grades. There are some very impressive grades if you take the time to research it. The intrinsic cost is often less, but life should be massively better. Consider also titanium grade 5.

Now to suggest titanium is getting silly, the working involved in just fabricating would be horrendous, have you ever tried to machine titanium? Considering many last a long time don’t think either 304 or 316 will be worse, as said it’s ofen the welding that’s the issue, we use both all the time with work and failures are mostly the welder using the wrong filler wire, difficult to tell at the time though

 

[Neeves]

It’s not good enough. 304 is junk, 316 is better junk. Buy 2205 or 2207 or better stainless grades. There are some very impressive grades if you take the time to research it. The intrinsic cost is often less, but life should be massively better. Consider also titanium grade 5.

The availability is a casting made from 304 or steel/iron. That is the choice. I think I could research for years, I've done a bit for this item - that is the choice. If you know of a source of 316 stainless elbows - please elaborate.

I used 2205 Duplex for my bridle plates. We have used Hardox steel, galvanised as well - I know my steels.

Jonathan

 

[Spirit (of Glenans)]

I don't know how they fabricate the flange in the cast steel version, the original Volvo elbow - but the flange inside or underneath the spigot corrodes. When I receive the 304 version I will give it more than a cursory look. We too have had the end plates on the muffler, I'm guessing 316 stainless, failing - the stainless tube and the dome shaped end plate look fine - its the weld that has failed. The Aliexpress 304 stainless elbow looks cast to me but I've only seen the same pictures that everyone else has seen - how they have fabricated the internal flange - maybe I'll find out.

The Aliexpress elbow is supplied with a gasket - what it is made from, no idea - it does not matter, I can make my own gasket. I made my last gasket from what looked like a very robust card - but made from what looked like aluminium flake. It was very difficult to cut. It could have been mica.....??

But whether 316 is better than 304 is a bit academic as the option is for 304. So the question is not is 316 better than 304 but is 304 better than cast steel (or cast iron?). Interestingly the original cast version does not fail from corrosion - and it is soaked with hot seawater every time it is used - the failure mode is that it blocks (or in my case it fails because I clear the blockage with acid and its the cleaning process that eventually causes failure - not hot seawater.

Tranona How did you solve your muffler problem - did you have it rewelded, buy a new one or move to a different design like a Vetus version?

The elbow will be an interesting exercise as I under stand that the same elbow is used on the MD20xx, the D1 and D2 (?) series of engines and the aliexrpess versions are cheaper than a cast steel version, from Volvo (though inconvenient to source).

Jonathan

Slight thread drift, but I replaced my VP muffler with one from Osculati. It's of the same design as the original, but somewhat easier on the wallet than the OEM item.
See the website linked below for details of the dimensions of the muffler range, plus a map showing locations of dealers:
Exhaust silencer Ø 51 mm

 

[Spirit (of Glenans)]

The availability is a casting made from 304 or steel/iron. That is the choice. I think I could research for years, I've done a bit for this item - that is the choice. If you know of a source of 316 stainless elbows - please elaborate.

I used 2205 Duplex for my bridle plates. We have used Hardox steel, galvanised as well - I know my steels.

Jonathan

The OP says the choice is between 304 and 316 . His attachments:
110.2￡ |Ap03 861906 21190094 Stainless Steel 304 Exhaust Elbow For Volvo Penta Md2010 Md2020 Md2030 - Exhaust Headers - AliExpress

Volvo Penta D2-40 stainless steel exhaust outlet kit

 

[lustyd]

With regard to 316 or 304 I would never use 304 on deck never mind below the waterline. Some recently purchased 316 cleats and tubing rust like it's going out of fashion. Can you imagine how bad 304 would be. If I could get none rusting s/s for on deck use like my original s/s fitting when the boat was manufactured I would be delighted

If you're getting rust that quickly it's likely the finish or some debris on the items assuming it's real 316. Give it a good clean and polish and should be better.

 

[geem]

If you're getting rust that quickly it's likely the finish or some debris on the items assuming it's real 316. Give it a good clean and polish and should be better.

The tubing is mirror polished as are the cleats. They get a regular soaking with saltwater and they rust for fun. I have polished them regularly. I can't stand looking at all the rust.
My original s/s is perfect. Any new s/s these days seems to be junk. If something is labelled as 316 how would the consumer know any different if it's an inferior quality? Apart from the rust maybe

 

[lustyd]

If that's the case then return them. Any stainless will rust if you leave it salty but if you're treating them well and they still rust they probably aren't the grade claimed.
My point was mostly that when new these things often rust because they aren't finished well and there is often a layer of metal dust on them.

 

[Spirit (of Glenans)]

But related

We will be installing a 304 elbow to the exhaust manifold - with a gasket between elbow and manifold. The studs are steel and I was going to use stainless nuts, greased.

Are there any issues of which I should be aware, primarily the nuts and the studs - and will the grease last anyway/

Jonathan

I note that the 304 item from Aliexpress includes a gasket, while the listing of the 316 item from Parts4engines recommends the purchase of a gasket as a separate item.

 

[lustyd]

I note that the 304 item from Aliexpress includes a gasket, while the listing of the 316 item from Parts4engines recommends the purchase of a gasket as a separate item.

Depends which one you buy, the MD2040 one includes the gasket on P4E

 

[geem]

If that's the case then return them. Any stainless will rust if you leave it salty but if you're treating them well and they still rust they probably aren't the grade claimed.
My point was mostly that when new these things often rust because they aren't finished well and there is often a layer of metal dust on them.

Tube was from Metals4U. It's now part of our guardrails supporting solar panels. We are 35nm from Venezuela in Curacao. How do you return them?
My original pulpit and pushpit are rust free and original to the boat. We see lots of modern cruisers with extensive rust on deck fittings. The poor quality of new s/s is not just my problem. My Swiss friend was saying just the other day that the s/s on his new FP catamaran is junk.

 

[lustyd]

No answer to that unfortunately, supply of quality stuff is a huge issue these days and vendors even in the uk don't seem to stand by their goods as they used to

 

[Neeves]

No answer to that unfortunately, supply of quality stuff is a huge issue these days and vendors even in the uk don't seem to stand by their goods as they used to

This is going 'off piste' but part of the problem is self inflicted. This is a very focussed list - but its part of what I know:

Who asks for sight of a test certificate on their chain? Whe worries that a well know shackle marked WLL 2t in the UK actually means 2 short tons, not 2 metric tons. Did a anyone worry when the tether hooks used by Clipper were totally inadequate (certainly Clipper believed what they were told and did not test them). There are constant complaints that windlass are made from aluminium castings within which the stainless bolts corrode - making dismantling an angle grinder event - its gone on for decades - the consumers flock to these disasters like jackals to a carcase. Wichard chain hooks are a joke - do Witchard remove them from chandler displays? There are some successes, Rocna anchors being one, Mantus removed their chain hook, eventually - but did they issue a recall... guess! The life of anchor chain is, part, dictated by the quality of the galvanising - have you ever asked for detail of the galvanising of chain, or even seen a specification for galvanising.

I know - I'm becoming a bore.

I know other people who have different fetish have different lists.

I also know, and sympathise, with geem - you cannot question everything

But maybe we should question more.

Jonathan

 

[Neeves]

As a supplementary to Jonathan’s recent thread, both AliExpress and Parts4Engines offer cast St St Exhaust Elbows. The photos look identical, but AliEx is grade 304, while Parts4Engines is grade 316.
1. does the grade matter in this application?
2. Is it likely that these elbows are made in different grades of stainless?

110.47￡ |Ap03 861906 21190094 Stainless Steel 304 Exhaust Elbow For Volvo Penta Md2010 Md2020 Md2030 - Exhaust Headers - AliExpress

Volvo Penta D2-40 stainless steel exhaust outlet kit

Be critical but I had not noted that the OP had the second link with what looks like an identical image of an exhaust elbow in 316 in comparison to the Aliexpress version in 304.

The question is then pertinent : Is the 316 version a better buy than the 304 version? The second question is also pertinent - considering the similarity of the images is it likely these are not one and the same product (would you question? who would know? how would you tell?).

The Parts4Engines 316 version is available in the UK and the Aliexpress 304 version available in China. The UK sourced 316 version costs A$400 (in the UK) and the 304 version slightly less than A$200 excluding freight. We negotiated a minor discount and a cheap courier freight from China with delivery 8-14 days. The UK price includes your VAT which I should be able to recover.

I'm a cheapskate and have opted for the 304 version (and or - I'm not sure that the stainless quality will take any difference..

Jonathan

edited - when I looked more deeply and found the prices for Parts4Engines were A$.

 

[Daydream believer]

My original s/s is perfect. Any new s/s these days seems to be junk. If something is labelled as 316 how would the consumer know any different if it's an inferior quality? Apart from the rust maybe

With all due respect That is not a very sensible comment. Stainless steel varies in specification & can be supplied in qualities to suit the task in hand. 316 comes in more than one grade. ie L , Ti & H.
If one purchases from an ISO registered supplier then one can expect to get what one orders. Going to the cheapest supplier from overseas (anywhere for that matter) with no previous knowledge of their systems for ensuring quality supply of the correct goods, is the consumers own risk.
If one orders a lower grade material, item, one cannot call it " junk". It is a lower grade ordered by the consumer. That does NOT make it junk. It is just not necessarily fit for the purpose the consumer thinks it is.
That is the result of the consumer's poor judgement

 

[Daydream believer]

Who asks for sight of a test certificate on their chain? .

I have on occasion. But then I sell the stuff, so want to know what I am selling. Over the last 20 years, a number of times I have had cheaper quotes for supply, but rejected, due to inadequate, or zero, test data. Even a test cert that on detailed examination did not match the chain I was being offered. The supplier was trying to pull the wool over my eyes. Not good when one is supplying it to 50 plus mooring holders to keep their pride & joy on.

 

[geem]

With all due respect That is not a very sensible comment. Stainless steel varies in specification & can be supplied in qualities to suit the task in hand. 316 comes in more than one grade. ie L , Ti & H.
If one purchases from an ISO registered supplier then one can expect to get what one orders. Going to the cheapest supplier from overseas (anywhere for that matter) with no previous knowledge of their systems for ensuring quality supply of the correct goods, is the consumers own risk.
If one orders a lower grade material, item, one cannot call it " junk". It is a lower grade ordered by the consumer. That does NOT make it junk. It is just not necessarily fit for the purpose the consumer thinks it is.
That is the result of the consumer's poor judgement

With all due respect, I ordered 316 tubing for marine use. It should meet a standard suitable for marine use. My original drawings for my boat say 316 grade. Nothing more needed saying. The original s/s doesn't corrode. Why does modern 316 corrode?
Why does my friend on his new cat describe the s/s fittings that a huge boat manufacturer installed as junk? It appears that it was not just me that expected 316 grade stainless to be suitable for marine use