MD2030 changing an exhaust elbow.

[MM5AHO]

After finding a lack of power at higher revs and a little smoke then too, my question about what might be the reason, was answered here by several as probably a blocked exhaust elbow.

Here's a few tips on doing this job.

In my engine bay there's not a lot of room, and access to the rear of the engine is difficult, but not impossible. The boat is a Rival 32, and the engine bay is under the companionway stairs. These are easily removed to give engine access, but the narrow engine bay still restricts the space available to swing a spanned.

There's an electric box beside the engine. This is best removed to improve access to the elbow holding bolts.

This is removed by two bolts and a screw through a tab. Remove the top black cover (shown removed above, 2 screws to remove), then remove the clear plastic box screwed to the side of this black box. Don't disconnect anything electrically, just let them hang loose. This will give better access to the two nuts holding the elbow on that side.

In this view the rubber boot that feeds water from the heat exchanger into the elbow is removed and two of the four nuts that hold the elbow can be seen.

Best way seems to be loosen the rubber boot's hoseclamps (3), then remove the elbow nuts, then take the whole thing off, elbow and boot together. It goes back on best this way too.
While you have it open, check that the tubes in the heat exchanger are not blocked. If they were, remove boot other end too and clean out.

Here's the elbow removed, with its short length of exhaust hose connected.

And here's a close up of the carbon deposit inside.

Note the tiny hole? All my exhaust was going out there. No wonder I couldn't get over 2000 rpm, and not a lot of power.

The inside of the rubber boot needed cleaning out too...

To reassemble, fit the boot to the elbow first, putting all the hoseclamps on. Its almost impossible to get the boot on afterward, but dead easy to do it first.
Make sure to have a new gasket, and to clean the face of the mating surface first. Use a chisel or similar.

When its fitted back and nuts tightened, the electric box can be refitted.
Next is a new piece of exhaust hose to join the elbow to the water trap.

Here's the gap between my exhaust elbow and the exhaust water trap. There doesn't seem a standard place for this to be so your hose might be different length. Mine is short, only 180mm of 45mm diameter hose.

I didn't take a piece of hose, so have to do that job tomorrow, but then hopefully I'll have my old faithful engine back to normal.

I fitted a new elbow. The old is not only carboned up but quite corroded. The carbon is very hard and difficult to move. The corrosion product is even harder!

So if you have to do this job on this engine, hope this helps someone.

 

[Mrnotming]

Great post Geoff,
Very useful, I will check mine this season!
I have about 2000 hours up, nearly all at 2700 RPM
May I enquire what is the cost of the elbow?

 

[yotter]

Geoff,
Excellent pictures and explanation. I had the same symptoms at the start of a season about 4 years ago on my previous boat (Sigma 33 with MD2020). When I eventually removed the elbow, I just could not believe how clogged it was.

My current boat ( Dufour34) has the MD 2030D, and surprisingly to me, the maintenance records from the previous owner show that the elbow was removed and cleaned. I think that at the end of this season I shall remove it and give it a decoke or at least an inspection.

I heard some time ago from Vyv Cox that Yachting Monthly may run an article on this at some point, and I sent him some photos, but I only used my fairly low spec mobile phone, so do not be surprised if there are requests for your very fine photographs.
Angus

 

[prv]

That's interesting - the elbow looks identical to the one on my D1-30; I wonder if they re-used the same part.

I did manage to clean mine out with a bath of fairly concentrated hydrochloric acid, and a screwdriver, but it was hard work.

Might try giving it an Italian tuneup at some point this season as well, it used to work well for Kindred Spirit's 2GM20.

Pete

 

[Stork_III]

That's interesting - the elbow looks identical to the one on my D1-30; I wonder if they re-used the same part.

I did manage to clean mine out with a bath of fairly concentrated hydrochloric acid, and a screwdriver, but it was hard work.

Might try giving it an Italian tuneup at some point this season as well, it used to work well for Kindred Spirit's 2GM20.

Pete

Same part number 861906

 

[J Neeves]

Geoff,

Nice work!

 

[neil1967]

Informative post. I understand why exhaust elbows deteriorate - a potent mixture of hot gases and seawater - but why do some engines seem to clog them up as well? My Perkins 4108 has about 4000 hours on it, and when I examined it recently there was only a light build-up of soot. I don't believe the previous owner would have replaced/cleaned it, so why the difference?

 

[vyv_cox]

A very nice pictorial account, thanks for posting it.

I can speculate on the reasons that some engines coke up and some don't. Condensation type deposits occur when hot gases containing some substance that is solid at lower temperatures come into contact with a cool surface. This is the main cause of bore glazing, not running the engine slowly but allowing it to warm up from cold slowly. In exhausts, if the engine is warmed up slowly because the boat is kept in a restricted place such as a long marina or river, the gases tend to condense on the seawater cooled surfaces if their velocity is low. When the engine is run hard this probably does not happen as there is insufficient time. The problem may well be worsened if the engine is run for only a few minutes before the sails are raised and it is turned off. The deposits are never burned off and accumulate steadily.

 

[J Neeves]

The deposits are primarily calcium (maybe magnesium), they dissolve in acid. If you drop a clogged elbow in acid the sedimentation, insoluble carbon, is pretty minimal. If there was a lot of carbon I would expect to see it in the exhaust gases as black smoke.

The seawater that passes through the heat exchanger will be heated by the exhaust gases in the elbow and an increase in temperature would normally increase the ability of water to contain dissolved solids. Changes in Ph will impact precipitation though why one engine will have precipitation and not another seems illogical. Why the precipitation 'sets' on the elbow, and fairly evenly (so there is no preferential settling, top or bottom) and does not flush out is another part of the mechanism.

There is a lot of dissolved calcium (and magnesium) in seawater, I believe in parts of the Gulf of Mexico it precipitates out naturally.

Calcium precipitates on our water intake pipes for our engine, if you crush or flex the pipes you can feel it 'crack' and we wash it out every service (and why it precipitates on a cold water intake is another mystery). I do not know if correct but someone (who was selling said exhaust elbows) said there was no problem with stainless elbows.

Whatever - its an excellent money spinner for Volvo. Its expensive for owners as we need to acid wash about every 1,000 hours and replace every 2,000 hours and most would simply replace (without acid washing).

Jonathan

 

[noelex]

Thanks Geoff.

Articles like this, especially those with lots of pictures, are a great help for those doing the job for the first time.

The only thing I would add is to have a very careful look for internal corrosion in the water jacket. This can in some circumstances let water into the engine.

 

[EdWingfield]

Well done Geoff, excellent explanatory. I replaced the elbow on a 2030 also but because it was 10 yrs old and worn out. An engineer told me these items don't last forever.

Your extraordinary pic of the carbon blockage will explain a cause of loss of power to many skippers.

 

[MM5AHO]

I've been away for the weekend, but did get the job completed on Saturday morning.
To enable the short length of hose to fit easily (and I was doing it myself), I smeared a little grease inside the hose, at each end. Very sparingly, and spread evenly. Pre place the hose camps on the hose, and lightly tighten so they don't fall in the bilge. REach in and slide the hose on the elbow, and on the other connector. In my case that's the exhaust pot/trap (prevents water flowing backwards into the engine, by limiting the volume that can flow backwards, trapping it in the pot).
The loosen and move the hoseclamps into position and tighten up. I use two clamps on each joint. Hoseclamps and not to expensive, but not failsafe either. Using two means a lower chance that I'd have to replace one at sea!

After connecting up, I started the engine and looked for leaks, both water and exhaust. Finding none, I allowed the engine to warm up fully before leaving the marina. If it were going to fail, this was the time.
When hot enough, I headed out for a short spin.
Previously, with the blocked elbow, 2000 rpm was max. Now it will do about 3600rpm flat out, faster that I remember it ever doing in my time.
So very pleased to have sorted that issue.

Still flabbergasted that an engine would run with that much of an exhaust restriction.

 

[SimonP85]

Last season one of the rubber boots developed a tiny split causing sea water to spray out into the engine bay. Amazingly no major damage other than a damp engine bay. The most frustrating part was waiting in Cherbourg for four days for the part to arrive and thereby ruining our plans for the trip - a Channel Island cruise turned into five days in Cherbourg!

Both boots are now replaced and we have a spare on board!