The SD is for South Dakota, which is where I was all the time a few years back. Now I’m only there a few months a year (unfortunately now in the winter with the Covid out on the loose) and spend most of my time somewhere on the East coast. I asked the question because going back to Marlow/Hunter you can’t get a solid answer, because they add that they didn’t build Hunters and or limited information on it, they listed my motor as a 56 hp, but by Yanmar its a 54hp. My OEM manual lists a 16” X 13 two blade, but they came with the 40hp or optional 54hp which is what I have. I running an 18” X 12, 3 blade now but don’t think I getting the speed I should be achieving, much better than 5 1/2 knots 2400 RPM (hull speed should be a little over 8 knots). Now I went over everything with Yanmar as for fuel filter, clean bottom, clean prop, not bent or dinged, clean fuel, I achieve maximum RPM of about 3300 RPM wide open throttle, (maximum RPM should be between 3250 and 3325) so I’m there. Only thing the speed is loaded, provisioned and I little heavier in the rear. The prop that’s on it was what it came with, I did talk to the company that made that prop (Michigan Wheel Marine) and they said that I should be running a 14 pitch and could even go up to a 15 pitch. I have also read the different prop reviews which showed about 1 1/2 knots difference between one mfg/design and another, I may just have one of those slow prop Mfg/designs.