Exhaust elbow, specifically MD2020

[Daydream believer]

It's possible to do it right, also. Like on keel cooled boats.

Of course . But how many would get it, "right"?

 

[seumask]

Parts 4 engines do one and they are generally pretty good and reasonably priced all IMHO £225 seems reasonable.
Check you don't need the high rise one which is much dearer and not usually available in stainless

Volvo Penta MD2020 Stainless steel exhaust outlet kit

Edit. See you are in Aus so UK supplier not much use, but the Aliexpress on does look rather similar to the Parts 4 Engines one above!

 

[Daydream believer]

I'm not impressed with the access to parts of the MD20xx engines - partially the engine and partially squeezing the engine Into a very confined space (the hull at the point of installation is not much more than the size of the engine).

I do not have an issue with access having changed the saildrive seal twice. I have changed item such as engine mounts, including an engine mount bracket that broke (50yds from my home berth after, 4 weeks away from home inc motoring up the Dutch canals) I have changed the alternator for service. The exhaust elbow & every year the filters & oil, as well as the raw water pump. I have changed numerous impellors & had the heat exchanger off for cleaning & checking.
The space is not massive but perfectly adequate for my 31 ft yacht. I think that the MD2020 is a very easy engine to work.

If one has a problem with access, I suggest that it is more to design of the boat than design of the engine
Having a decent set of tools ready to hand, that fit all the nuts & bolts & which are not covered in rust is a good start, when working on any engine. Trying to get by with a set of mole grips, a bent screwdriver & an adjustable spanner does not cut it.

 

[CJ13]

The elbow from AilExpress is 304. The parts4engines elbow says it’s 316, though the picture looks identical.
Is the grade of stainless important?

 

[BabaYaga]

If the deposition is, as I elude, a calcium deposit then the mechanism is a chemical process within the elbow - the calcium comes from seawater (and it maybe a calcium and magnesium deposit). It is difficult to envisage why stainless would reduce this deposition, unless something in the cast iron acts as a catalyst. But if it is a thermo-chemical process then running the engine, not under load, should not make any difference......? Calcium deposition also occurs on the water intake hoses - which you can clear by beating the hoses on a hard surface and then flushing them clean. Calcium and magnesium in seawater is common and in some parts of the world the water is saturated and there is a natural deposition (which would eventually form limestone or dolomite). There are facilities round the world extracting magnesium from seawater or brine - its common place (think Hartlepool between 1940 and 2000 - ish where 100,000s of tons were extracted). Think also of furring of your kettle (in the absence of a water softener).

I would not say that the calcium theory necessarily is wrong, but I am pretty sure it is not what partly blocked up my stainless steel exhaust elbow, see photo below.
This high riser elbow has been on my Beta engine since new, 2006. The construction is such that last 80mm or so is sleeved, so the cooling water only enters the space surrounding exhaust pipe. Sea water and exhaust gas doesn't mix until down in the hose.
Still I found this build up first time I took the bend off about five years ago. Very difficult to remove, I can only think it was carbon. I also found some pitting/cracking in the inner sleeve and ended up replacing the elbow with similar part from my Beta dealer.

 

[Neeves]

My analysis of the choking of the elbow being calcium is based on the simple fact it dissolves in acid whereas carbon is inert. It may of course be a large percentage of carbon bonded with a very small percentage of calcium.

But it does dissolve in acid and I found I can remove the blockage and reuse the elbow once. The second time there is sufficient corrosion of the steel that the acid removes the internal baffle.

I have not examined the internal of a new elbow but there appears to be a baffle under the spigot (inside the elbow) that, my guess is, it spreads the seawater to better mix with the exhaust gases. I assume it there to cool the exhaust. The baffle suffers corrosion and is the final cause of failure of the elbow.

Removal of the elbow is difficult simply because there is very poor access to the 4 nuts that secure the elbow to the 4 studs in the engine casting. There is simply insufficientt space to locate a conventional ring spanner or socket onto the nuts. It does not matter how good your tools are - if you cannot locate your spanner or socket squarely onto the nuts. If you do your home work prior to addressing the problem physically then every you tube video of disassembly of the Volvo elbow says exactly the same thing - access to the 4 nuts is appalling. Once you break the seal - they are easier - its cracking the nuts that is the issue. Once you have them loosened its easy - and I cut down a spanner to 30mm length to allow easier rotation of the nuts - as space is limited to swing a conventionally long spanner. There is exactly the same issue with removal of the water pump - insufficient room to swing a spanner - so my chopped down spanner serves to remove to key items - once the nuts are loosened.

Jonathan

 

[vic008]

P4Engines is about 7 day to NZ
Never thought to check AliExpress, but cant find one for a VP2003 anyway.

 

[Beneteau381]

Every thread on issues with an exhaust elbow and specifically the MD20 series (but I also believe the newer D1 series) mentions the difficulties of removal and the blocking of the elbow with a deposit, erroneously described as carbon but actually calcium hydroxide or carbonate pigmented with carbon.

The deposit can be removed with acid (proving that it is not carbon) but the acid also attacks the steel or the casting and I have found you can only acid treat once (and it is very messy)

If the elbow did not block there would be no need to remove it - and then the whole issues would go away. Not entirely true as the cast versions do corrode - but they block more frequently than corrode - so corrosion is not a big issue.

Along with the above the other oft repeated comment is to replace the elbow with a stainless version, or which there are a number of entrepeneurs out there making them. A google search also throws up pictures of what look like cast stainless version - identical to the cast iron or steel versions - looking very professional.

Despite the constant mention of replacing with a stainless version I have never seen a back up report suggesting they offer any solutions to the issues of the genuine cast version. The water intake (spigot) on the cast version seems to have a baffle inside, to spread the water? - and this baffle, or its method of attachment does corrode (and many stainless items corrode where there is any welding).

I've just removed my exhaust elbow (another interesting story) but I need to replace the elbow and am wondering whether to go down the stainless route or stick with the original cast version.

Do stainless elbows last longer? do they somehow stop the calcium build up,? are they corrosion free? - basically are they worth the money.

Any background

Jonathan


I have read, on this forum, that part of the problem is caused by running the engine under low load, say to recharge batteries.

If the deposition is, as I elude, a calcium deposit then the mechanism is a chemical process within the elbow - the calcium comes from seawater (and it maybe a calcium and magnesium deposit). It is difficult to envisage why stainless would reduce this deposition, unless something in the cast iron acts as a catalyst. But if it is a thermo-chemical process then running the engine, not under load, should not make any difference......? Calcium deposition also occurs on the water intake hoses - which you can clear by beating the hoses on a hard surface and then flushing them clean. Calcium and magnesium in seawater is common and in some parts of the world the water is saturated and there is a natural deposition (which would eventually form limestone or dolomite). There are facilities round the world extracting magnesium from seawater or brine - its common place (think Hartlepool between 1940 and 2000 - ish where 100,000s of tons were extracted). Think also of furring of your kettle (in the absence of a water softener).

I made one for my MD22 10years ago from SS threaded pipe parts and an ASAP mixer. Still going strong.

 

[gregcope]

Check you don't need the high rise one which is much dearer and not usually available in stainless

I have not found one yet.

I have contacted a few people, but struggling to get a quote or progress ...

 

[typhoonNige]

I’ve got a spare brand-new gasket for the exhaust elbow if you or anyone is interested? It was kicking around on my spares and as I no longer have a Volvo 20 series engine I don’t need it.

I’m interested the gasket John. Is it still available?

 

[john_morris_uk]

I’m interested the gasket John. Is it still available?

Send me your address by pm and I’ll stick it in the post.

 

[Tranona]

P4Engines is about 7 day to NZ
Never thought to check AliExpress, but cant find one for a VP2003 anyway.

That is because the 2003 does not suffer from this problem to the same extent plus the number of engines in use is tiny compared with the replacement 20X0 series than ran from the late 80s to 2005 and the D1 range which is still current uses the same design.

 

[Dipper]

I can't answer your question regarding build up of deposits in the elbow but I bought a stainless steel one for my 2001 from HDI Marine in the USA via eBay. Your elbow appears to be available from them but it is more expensive than the Alibaba version. All I can say is that mine was beautifully made and fitted perfectly. I don't use the boat engine enough to comment on whether it will clog in the future or not.

V878 Stainless Steel Exhaust Elbow Replaces Volvo Penta Perkins P/N 861906 | eBay

 

[typhoonNige]

Send me your address by pm and I’ll stick it in the post.

PM sent

 

[Neeves]

I can't answer your question regarding build up of deposits in the elbow but I bought a stainless steel one for my 2001 from HDI Marine in the USA via eBay. Your elbow appears to be available from them but it is more expensive than the Alibaba version. All I can say is that mine was beautifully made and fitted perfectly. I don't use the boat engine enough to comment on whether it will clog in the future or not.

V878 Stainless Steel Exhaust Elbow Replaces Volvo Penta Perkins P/N 861906 | eBay

They do seem to have sold an interesting number of elbows.

Jonathan