Coked Up Exhaust Elbow

[ducked]

If it is carbon, you ought to be able to burn it out

Here I've got burning bamboo charcoal inside an exhaust manifold and an blowing through it with a hairdryer. It got pretty hot, but I was trying to loosen that stud rather than burn off coke, since there wasn't any.

 

[riverteign]

I removed my stainless elbow this year on a D2-40 after ~250 hours of use. It was clean as a whistle. I've no idea why it should be so much better than the original other than maybe the internal corrosion was catching the soot as it went past on the cast one. Whatever the reason, the original is a bad design and the stainless one is a good investment.

 

[Jon magowan]

Thanks ‘riverteign’ and all others who have responded.

I have a new stainless elbow from eBay. Hopefully that will sort the issue for the foreseeable future.

 

[Tranona]

Thanks ‘riverteign’ and all others who have responded.

I have a new stainless elbow from eBay. Hopefully that will sort the issue for the foreseeable future.

Good move - remember to give the engine some hard running from time to time. I found 2200rpm comfortable with my Bavaria and the prop allowed it to max at 3200rpm for the last few minutes., enough to burn off the deposits that build up.

 

[LittleSister]

If it is carbon, you ought to be able to burn it out

Here I've got burning bamboo charcoal inside an exhaust manifold and an blowing through it with a hairdryer. It got pretty hot, but I was trying to loosen that stud rather than burn off coke, since there wasn't any.

Reminds me that I read years ago that you could de-coke two-stroke motorbike exhaust pipes by shoving a lighted oxy-acetylene torch up one end, once the crud has caught light you turn off the acetylene but leave on the oxygen, and once it stopped burning the crud was gone and Bob, it was said, was your uncle.

I never saw it done (heaven knows what it would do to the exterior chrome plating!), and don't know if that would work on the presumably different composition crud in a blocked diesel exhaust elbow.

 

[Neeves]

It won't be acid once reaction has taken place (unless using excessive volume). It will be metal chloride and carbon dioxide. A bit more chloride in the sea will have little effect.

I believe the composition of marine scale is largely magnesium rather than calcium carbonate. Dilute hydrochloric acid removes it almost instantaneously. Only needs a few millilitres dripped onto the scale.

It could well be magnesium, same family as Ca on the periodic table. It was extracted from seawater at Hartlepool (and plants all over the world) but the MgOH was precipitated by dissolving Ca (at Hartlepool they used Dolomite rather than lime stone) in the seawater and the Ca replaced the Mg.

If you have a heavily blocked elbow dripping a few drops of acid is going to take a long time to clean it - I simply submerged the elbow in a bucket of acid leaving it overnight - I had no idea if the resultant liquor was still acidic (and I was not going to taste it to find out). The waste liquor is full of carbon - not sure it will have no effect in seawater.

I imagine the ideal is to remove the elbow when you do a full service, then you could drip acid on the inner surfaces and simply keep it clean. But using acid is nasty stuff - the less you handle it the better.

I don't quite understand why its a big issue with Volvo and not with other engines.

Jonathan.

 

[lustyd]

Whatever the reason, the original is a bad design and the stainless one is a good investment

It’s funny, only this week I had a lecture from a supplier on why I must fit the original and the dangers of stainless aftermarket ones.
Apparently stainless “causes electrolysis”, will crack and explode, and will most likely drip onto the heat exchanger causing it to corrode.
My partner was standing next to me and quite concerned by the time we left where I had to explain how hard it was to keep a straight face

 

[john_morris_uk]

It’s funny, only this week I had a lecture from a supplier on why I must fit the original and the dangers of stainless aftermarket ones.
Apparently stainless “causes electrolysis”, will crack and explode, and will most likely drip onto the heat exchanger causing it to corrode.
My partner was standing next to me and quite concerned by the time we left where I had to explain how hard it was to keep a straight face

Ah the salesperson talking complete bollocks routine.

I appreciate that I worked in research at the Royal Radar Establishment quite a long time ago but I do remember something about radars and how they work and how radar return signals are processed. At a boat show a couple of years ago I had to listen to a salesman trying to explain to me how vastly superior their latest radar was that he was trying to sell me. He talked complete and utter nonsense! I also had to keep a straight face.

Lots of examples available from others I expect.

 

[geem]

Ah the salesperson talking complete bollocks routine.

I appreciate that I worked in research at the Royal Radar Establishment quite a long time ago but I do remember something about radars and how they work and how radar return signals are processed. At a boat show a couple of years ago I had to listen to a salesman trying to explain to me how vastly superior their latest radar was that he was trying to sell me. He talked complete and utter nonsense! I also had to keep a straight face.

Lots of examples available from others I expect.

I actually had a chat to a Raymarine dealer who told me the new chirp radars are a waste of money unless you want a load of pointless gimmicks. I quite like him

 

[nevis768]

Volvo Penta D1-30f (750 hrs)

I’ve just removed the exhaust elbow from my engine, because I was struggling to get more than 2500rpm.

Looks like it was badly coked up with just a tiny hole remaining in the exhaust. I guess the previous owner only ever ran the engine at consistently low revs ?

Anyway, my question is, how much effort do I need to put into cleaning the exhaust port on the engine and how far should I be poking my screwdriver to clean it out ?

Should I be worried about any other coking up anywhere else in the engine ?

As always, very grateful in anticipation of your advice !

It's not just a blocked up exhaust elbow which could cause a reduction in revs, a barnacled propeller will do the same.