The one time so far that I motored her along underway, the engine was not warmed up well, but still blew quite a bit of black smoke at higher throttle settings. The prop, shaft and bottom are clean (this was on the way from the travel lift
to the slip about 1/2 mile away). Again, I have no idea what the rpm is - I have no tach. That is something I would like to add, but not sure how yet to do that on a Farymann - low priority anyway.
I felt at the time that the engine was overloaded even underway, but then again I am not sure. We used to have a small compactor called a "Rammax" that used the same engine and it always blew black smoke no matter what.
Maybe my first thing to do would be to install a tach and go from there?
BTW -I understand pretty well the characteristics of diesel
engines - I ran heavy equipment
for about 25 years before moving into the technology field.