Well, your direct experience may well be more valid than my hearsay. I've
spent 30 plus years around people who run big diesels for a living and I'm
just inferring from the gripes I've heard.

It may also be that fisherman, tug boat operators, and the like run their
engines a lot harder and longer. I certainly see more black smoke coming
out of the exhausts of commercial boats than yachts. The ones that stick in
my memory may also simply have been wrong about what was ailing their
engines.

I've never had the opportunity to see the inside of an abused diesel
cylinder at overhaul but the impressive build up's I've seen in aircraft
engines make it pretty easy to believe that carbon could effect the spray
pattern out of an injector without reducing it. You would think that
nothing could survive in the environment of an internal combustion engine
cylinder but physics are strange. If there is dust on the wings of your
airplane before you take off, a lot of it will still be there when you land.

--
Roger Long