Exhaust elbow/exhaust query once again!

[ICENI]

My new to me (purchased late 2019) Bavaria 32 (with MD2020 engine) I have now moved from her location in Cornwall to my Suffolk mooring and now she is ashore, I am tackling the important jobs.

The engine, according to the engine control panel has run 925 hours and looking at the general condition of both the boat and the engine I would assume that is correct.   Nevertheless I felt I should clean or replace the exhaust elbow.

I have checked the exhaust output each time I have run the engine and at no time was there any audible sound to draw one's attention to defective cooling.    However as soon as I could I removed the elbow.

As suspected there was rust and some blockage to both the exhaust and the cooling water intake.

What I am asking about is what I found at the junction of the exhaust manifold and the elbow (please see attached image)

As I have limited knowledge of marine diesel engines I wanted to check things.   The deposit had some salt residue as one would suspect but the rest of the deposit concerns me.   It is more than dust (sort of granules?) and I wondered if historically there had been some problem with the waterpump and the resultant black residue is the remains of a shredded impeller?   

The deposit sat in a position before the cooling water entered the elbow.

Next time when I am at the boat, I have a small vacuum cleaner and I intend sucking the exhaust to remove anymore residue I was unable to remove.

Any help/advice here would be much appreciated please?

[Yngmar]

That looks like mostly salt crystals, with a bit of rust and carbon deposits. Nothing unexpected in an exhaust elbow. The elbows do eventually need replacing (aftermarket stainless steel versions are available).

The MD2020 elbow is not a great design in terms of deflecting water the right way, so it's probably not unexpected to find some of this before the water injection point - but it if it goes back into the HE, check for blockages down the line.

Impellers normally just lose entire blades, which do not fit through the heat exchanger tube stack, so you wouldn't see them there and they would be in the wet part and get flushed out.

[ICENI]

Thankyou Yngmar,

Quite a relief!

I think the way to go is to bite the bullet and buy the stainless steel elbow.

Kind regards,

Chris.

[IslandAlchemy]

Common thing I'm afraid.  Left un-checked it will eventually cause problems.

Stick a new stainless elbow on there, and then remove and clean out every couple of years and all should be ok.

[Brian]

My elbow lasted 15 years before it needed replacing.  Unless it is seriously worn I would leave it as it is an expensive item to replace.