MD2020 black smoke & no revs

[Ric]

MD2020 worked fine ten days ago, but this morning would not rev abouve 1100 rpm, accompanied with black smoke.

There was an identical thread about this a few weeks ago (which has now been archived), hence I suspect that it is a blocked exhaust elbow.

What is involved in fixing this? Is it a major job or relatively easy DIY? Also, grateful for any explanation on what exhaust elbow does. I understand that cooling water enters the elbow, but not sure thereafter how the exhaust works.

 

[sailorman]

MD2020 worked fine ten days ago, but this morning would not rev abouve 1100 rpm, accompanied with black smoke.

There was an identical thread about this a few weeks ago (which has now been archived), hence I suspect that it is a blocked exhaust elbow.

What is involved in fixing this? Is it a major job or relatively easy DIY? Also, grateful for any explanation on what exhaust elbow does. I understand that cooling water enters the elbow, but not sure thereafter how the exhaust works.

what rpm out of gear

 

[bert49uk]

as sailor man says try it out of gear, you could have a fouled prop

 

[Ric]

Trying out of gear was first thing I did. No different.

 

[sailorman]

Trying out of gear was first thing I did. No different.

Not the prop over loaded then

exhaust elbow mix`s water with exhaust gasses to cool them

 

[vyv_cox]

What is involved in fixing this? Is it a major job or relatively easy DIY? Also, grateful for any explanation on what exhaust elbow does. I understand that cooling water enters the elbow, but not sure thereafter how the exhaust works.

The manifold is the point at which the seawater needed to cool the exhaust system is introduced into the exhaust gas stream. No moving parts or complications, just simple plumbing. All that is needed is to unbolt the manifold from the cylinder, disconnect the water injection fitting(s) and pull the manifold away. The salt deposits will then be clearly visible in the manifold and probably the head. It may make it easier to take the exhaust hose off the manifold but this is not strictly necessary.

Volvo water fittings are notoriously awkward and you will probably need new O-rings for them. A new exhaust gasket is usually recommended but is probably not essential.

I will be posting photographs from the post that you mention on my website in the next couple of days.

 

[jonathanhsm]

Taking off exhaust elbow is easy - just four nuts and obviously the jubilee connections to the flexible exhaust hose and the input hose. There is a gasket between elbow and block you will need to replace - its relatively cheap. The elbow may well be filled with black crud which you should get out as best you can with teaspoon - blunt screwdriver without holing the side. The water runs through a "jacket" on the outside of the fume tube bit. You can leave it in various chemical to soak (others will I'm sure advise.) If you need a new one they are xxxxxx expensive.

 

[Stork_III]

MD2020 worked fine ten days ago, but this morning would not rev abouve 1100 rpm, accompanied with black smoke.

There was an identical thread about this a few weeks ago (which has now been archived), hence I suspect that it is a blocked exhaust elbow.

What is involved in fixing this? Is it a major job or relatively easy DIY? Also, grateful for any explanation on what exhaust elbow does. I understand that cooling water enters the elbow, but not sure thereafter how the exhaust works.

I have Bumped a recent previous thread, is that the one you are referring. Threads are not archived just fade further down the list. I had similar problem, one day fine, next day black smoke no power coming out of Deben over the bar. Seems to become critical quickly. New exhaustelbow £173 see here When I tried cleaning mine, crudded up leaving 6mm opening, inner pipe broke free and new elbow needed.

 

[Neeves]

We found soaking in acid, worked a treat (but depends). The exhaust elbow is commonly blocked with calcium carbonate - it does not look like chalk as its black from exhaust soot - so acid works. If the elbow is 'old' you can eat though the elbow as quickly as the calcium carbonate - but there is no real alternative. We found that we can clean an elbow once, after that you need a new elbow. Elbows are dead simple and cost the earth - it is possible Volvo make no money selling new engines but generate profits from elbows and other spare parts. Castings are cheap - not Stg 175. One day some smart guy in China is going to cut the rug from under Volvo and sell exhaust elbows at Stg17.50 (that's about what they are worth).

I'd check - after we had shelled out for 2 elbows (we have a cat and had acid soaked them already and the 2nd time produced holes in the elbows) we then found out that stainless elbows could be bought more cheaply (but that's in labour expensive Oz.

Elbows are dead simple to remove, get stuck in! You will be amazed at how small the hole is in your elbow.

Why Volvo do not have a check of elbows in their maintenace manual is a real mystery, if not negligent - and the problem is very well known.

Jonathan

 

[charles_reed]

We found soaking in acid, worked a treat (but depends). The exhaust elbow is commonly blocked with calcium carbonate - it does not look like chalk as its black from exhaust soot - so acid works. If the elbow is 'old' you can eat though the elbow as quickly as the calcium carbonate - but there is no real alternative. We found that we can clean an elbow once, after that you need a new elbow. Elbows are dead simple and cost the earth - it is possible Volvo make no money selling new engines but generate profits from elbows and other spare parts. Castings are cheap - not Stg 175. One day some smart guy in China is going to cut the rug from under Volvo and sell exhaust elbows at Stg17.50 (that's about what they are worth).

I'd check - after we had shelled out for 2 elbows (we have a cat and had acid soaked them already and the 2nd time produced holes in the elbows) we then found out that stainless elbows could be bought more cheaply (but that's in labour expensive Oz.

Elbows are dead simple to remove, get stuck in! You will be amazed at how small the hole is in your elbow.

Why Volvo do not have a check of elbows in their maintenace manual is a real mystery, if not negligent - and the problem is very well known.

Jonathan

Yanmar, recognising the need for just such a check, include it as part of the 1000 hr service.

It's usually cheaper to have replacement elbows made up locally, from stainless steel than to buy the makers' replacement (either Yanmar or Volvo). Unfortunately the stainless ones don't last for ever either.

If you use sulphamic acid, rather than a strong solution of a mineral acid, you can reduce the damage done, but still have to use mechanical scraping to get out the crud.

 

[Gymnopedie]

2020 black smoke and no revs

Last weekend I gave my 13-year-old MD2020 a "birthday" in anticipation of some extended cruising this season and apart from the usual oil/filter/impellor changes I checked the heat exchange etc.

The copper tubes were generally clean but had a slightly greasy deposit which was easily cleared with soapy water. The exhaust elbow was easily removed and most pleasingly had only v. light carbon deposits, no caking or diameter reduction and no corrosion. Straight back together and no leaks (using old gasket).

I suppose one day the stern tube seal will need replacement but no signs of trouble yet!