Ditto, but I'd add another--soot buildup in the mixing elbow (where the exhaust gases cool down). Get enough in there and the engine falters.
Please correct me if I am wrong.
Carbon buildup is BAD. I noted earlier that it was said that you just punch it every once in a while and clean it out. My undersatnding, although there is some fact to that, is not entirely the same.
The mixing elbow was mentioned so I will start there as I have had to deal with high backpressure issues (not on my boat) - but seemed to have gotten quite an education.
If you are getting high back pressure, the rear cylinders will get hot. You will also get a carbon buildup in those cylinders. That carbon then slowly scores the cylinder walls. That in turn causes a compression loss. Compression loss then causes engine performance loss and finally total failure.
That is why you do not run your engine for long periods of time at low RPM's. Please explain where I am wrong. THis is what has been explained to me by Mastery, Boatswain, Yanmar, Valiant, and many other marine engine specialists that had to get involved. In essence, it is the reason that running your engine without a load is a bad idea - carbon buildup.
One of the key tests for a diesel's health is a compression test. Each of the cylinders should be within 10% (depending upon the engine) of each other. If they are not, there is an issue somewhere. I know that we found many rear cylinder failures due to carbon buildup due to a mixing elbox without the proper sized exaust tubing.
Again, I do not pretend to be a diesel mechanic, just repeating what I have learned and been told over the years. Carbon buildup and cylinder scoring is like diesel cancer, a slow, quiet killer.
Just an edit and feel fre to jump in: Not running at a load causes the cylinders to not have the proper backpressure and will cause scoring.