I have a D1-30 and previously had a 2030 in my boat, so i assume the experience would be similar. In practical terms I cannot say there is much difference although the D1-30 is slightly slower revving.
I had a D1-30 and now have a boat with a 2020, both saildrive. I do not think there is a lot of difference mechanically but some in the electrics and peripherals, they both have the oil filter horizontally on the starboard side, how awkward that proves to be will depend on the boat. Both seem to be powerful for their quoted hp and the 2020 is remarkably frugal with diesel. Our D1-30 burned 2l. per hr at 6kts but if you pushed hard against a tide (at max. around 71/2kts. in our case) you could get rid of nearly 7 litres per hr. Both really need a decent prop. to performto their potential. The indirect cooling system in our 2020 is a bit simpler without a separate header tank and changing the coolant can be awkward. I like both engines,the 2020 may be slightly less complex but the D series are modified Perkins industrial motors so should be reliable. In summary the D series is a more recent version of the 2020 but without that much difference, I would be happy with one.
