There are some TM's that will run on either, but I don't think the MK is one of them. I could be wrong though.
As for your boat Pete, I have a 55PD on mine, and although it works pretty good, I want more power. I'd like a 70lb 24volt.
Mine will troll my boat to 2mph on a calm day, but if its windy at all, I have a hard time keeping it going 1.5mph into the wind. I usually have to motor up wind, and troll back with the wind.
Its fine for positioning the boat, but if you want to troll at all with it, go bigger than 55lbs.
P.S I also have a 16ft deep and wide tiller with 40hp.
S.