Main reason for changing your oil is because of the products of combustion and other impurities that get into the oil. Used oil has traces of metal elements from bearings wearing and even from the castings on newer engines. These impurities in a diesel engine, when burned with fuel, end up being deposited on piston crowns and turbocharger blades. The residual bunker fuels used on diesel ships are tested for used lube oils and would be rejected if found. Due to the high costs of reclaiming used lube oils these often found their way into ship fuels.
I wouldnt do it on your boat. The oil has additives in it that can be harmful to the engine when burned. I have done it on ships as well, but only when your adding a couple hundred gallons of lube oil to tens of thousands of gallons of heavy fuel oil. Anyway, dont do it on your boat, its bad idea in my opinions.