Exhaust elbow

[38mess]

I took ours off and it's clogged up with hard black deposits. I don't want to damage the elbow by chiseling it out.
Can it be soaked in something to make the deposit softer?

 

[oldgit]

..................attempted to de- clog this MoBo riser .


this one simply fell to bits on removal

 

[mjcoon]

I took ours off and it's clogged up with hard black deposits. I don't want to damage the elbow by chiseling it out.
Can it be soaked in something to make the deposit softer?

Liquid oxygen? (Most things will burn off with that assistance!) Or whatever is recommended for engine decoking?

 

[Bandit]

I have just replaced my injection bends in a mobo for the second time at age of about 10 years each time, this last one was the cause of an overheat as the water flow was so reduced due to the blockage in the bend of about 75%.

The blockage is rust and rust flakes also the lip of the bend that the hose sits on is also corroded so difficult to get a seal.

On yacht engines you often see the bend's cracking or perforating.

It is better to replace with new.

 

[Tranona]

Essentially no. It is baked on hydrocarbons which are resistant to chemicals. You will also probably find that when you chip it away the iron underneath is corroded and like the examples above your chisel or whatever will go straight through.

10000 hours is end of life so get a new one to give your "new" a good start for its second life.

 

[seumask]

I tried vigorous use of a screw driver on our previous cast one ( MD2040), soon ended up with a hole in it! Casting appears to have been turned to a metal form of cheese so I would strongly suggest you expect to replace it if you try mechanical cleaning, and the fact that it broke relatively easy suggests that its mechanical properties were much depleted by the crud in it!

 

[38mess]

Essentially no. It is baked on hydrocarbons which are resistant to chemicals. You will also probably find that when you chip it away the iron underneath is corroded and like the examples above your chisel or whatever will go straight through.

10000 hours is end of life so get a new one to give your "new" a good start for its second life.

Good advice.
This morning whilst waiting for the 'new' engine to arrive I thought I would tackle the elbow. It's now in the skip, even the water hole at the top was solid with crud, No wonder the engine died. I never thought to put the elbow on the regular maintenance schedule. I'll see what the one on the new engine is like before I shell out for a new one.

 

[NormanS]

Two or three years ago I was suspicious of mine, on an MD22, so bought a replacement. When it came, I was surprised to find that was cast alloy. It seems to be alright, and I've taken it off a couple of times to inspect it. Has anyone experience of a cast alloy exhaust elbow?

 

[ChromeDome]

this one simply fell to bits on removal

Geeez, I do not miss green lumps in the engine room

 

[Blueboatman]

Two or three years ago I was suspicious of mine, on an MD22, so bought a replacement. When it came, I was surprised to find that was cast alloy. It seems to be alright, and I've taken it off a couple of times to inspect it. Has anyone experience of a cast alloy exhaust elbow?

I think the yanmar hi rise one was a bronze casting. Chipped out ok anyway.
The brass threaded water inlet spigot was dezinced/wasted though and replaced …
Mild steel threaded riser pipe,
so many metals !

 

[gordmac]

Geeez, I do not miss green lumps in the engine room

I am not convinced VP know what a metallurgist is!

 

[Tranona]

I am not convinced VP know what a metallurgist is!

The problem with the exhaust elbow in this case is nothing to do with the material, which is cast iron, but to do partly with the design and partly due to the way most engines are used. it is not the only make or type of engine, nor material that suffers from similar problems.

 

[Zagato]

You could buy stainless steel exhaust elbows from America years ago for Yanmars. It's not the ultimate answer as even high grade SS will corrode eventually but it is an improvement. This problem is well known and there are many rebuilt engines out there!

 

[SaltyC]

Guilty as charged!

Never thought about exhaust blocking, no problems for many years until wife was ill, 1 season leave marina, tick over in sealock, depart hoist sails, race and repeat to return. All season no 'hard' motoring.

After winter haul out upon relaunch, tides right, back to berth, fit jib and leave harbour.

Max speed upon leaving outer harbour 2 knots, more throttle more black smoke.

Upon investigation we found an exhaust elbow with a pencil sized hoile!!! Volvo MD2020

 

[Tranona]

Perfect illustration of what happens.

Compare with my first MD 2030 in my charter boat in the Ionian. out around120-140 days each summer. Morning 4 hours motoring (no wind) at 2400 to keep the beers cool, heat the water and get to lunch stop and a sim, afternoon, 3 hours sailing one hour motoring (sometimes all motoring) to get to overnight stop. Rest of year laid up. 3500 hours over 10 years including couple of long distance delivery trips mostly under motor and long trip to Spain again mostly under motor. Original elbow, engine performance same as from new in terms of fuel, oil and overall refinement..

 

[SaltyC]

Perfect illustration of what happens.































Compare with my first MD 2030 in my charter boat in the Ionian. out around120-140 days each summer. Morning 4 hours motoring (no wind) at 2400 to keep the beers cool, heat the water and get to lunch stop and a sim, afternoon, 3 hours sailing one hour motoring (sometimes all motoring) to get to overnight stop. Rest of year laid up. 3500 hours over 10 years including couple of long distance delivery trips mostly under motor and long trip to Spain again mostly under motor. Original elbow, engine performance same as from new in terms of fuel, oil and overall refinement..



















We too haofno problems for 6 years of 'normal' cruising use, however, 2 years of pottering due to health problems.......

No problems for the next 6.

So, lessons engine needs to work and run at > 2000rpm regularly for a reasonable period.

Interestingly, I now have a Yanmar and they state engine should be 'Blasted?' To max revs (governor limit) 5 times before stopping to clear exhaust.

Goes against my mechanical sympathies.

 

[38mess]

The 'new' engine arrived today. The exhaust elbow looks ok, a bit of crud, but I have ordered a stainless one just to be on the safe side.

 

[Bandit]

Stainless gives you a whole raft of different corrosion problems! Not necessarily better .

My engines 370 hp injection cast iron bends bends last about 10 years before causing problems, A boat we looked after twin 500hp Volvo Pentas had Halyard stainless injection bends we replaced them every 5 years and the latter cost a fortune.

 

[38mess]

Stainless gives you a whole raft of different corrosion problems! Not necessarily better .

My engines 370 hp injection cast iron bends bends last about 10 years before causing problems, A boat we looked after twin 500hp Volvo Pentas had Halyard stainless injection bends we replaced them every 5 years and the latter cost a fortune.

Only stainless available unfortunately

 

[rotrax]

Having had much experience of carbon blocked two stroke exhausts, when I removed the Kiwi made S/S one from our Bukh DV20 I soaked it in a strong Caustic Soda solution for 48 hours.

A gentle poke with a small spike and a good hose out and it cleaned up like new.

Dont, repeat, Dont, put an aluminium exhaust elbow, or anything else aluminium, in Caustic Soda.

It dissapears..................................................