The two stroke diesel isn't really comparable to typical two stroke gas engine ala. chainsaws and dirtbikes. Because they use forced induction, they don't use

The two stroke diesel isn't really comparable to typical two stroke gas engine ala. chainsaws and dirtbikes. Because they use forced induction, they don't use the crankcase for scavenging and thus have a "normal" four stroke style oil sump. Since the total loss lubrication system isn't used, they aren't actually any dirtier on principle than a four stroke. The big ship engines also turn very slow so a lot of the physics behind it is different, and different fuels are used compared to road going diesel (different grades of bunker fuel). You are correct that GM used to make a two stroke diesel for over the highway and medium-sized equipment use but they were phased out because they weren't competitive on fuel consumption and their crude superchargers were incredibly loud. Growing up my Dad owned a compactor with one and I'd have to wear ear plugs under my ear muffs to not be deafed by "the screaming jimmy" (Detroit 471, IIRC).