Well, a lot of surprises. First of all, we found the manual, which shows a lot of the information I was working off — mostly gleaned from boat dealer websites — was incorrect.
The Mark 2C we have is 12'6" (3.8m), with a maximum recommended power of 25HP (and maximum allowed = 35HP).
I was looking at information for the Mark 2, which is 13'9" (4.2m). (Apparently the "Classic" name came after this year).
The long/short debate is null, as we had ordered a 25HP Mercury that is just too heavy for the boat. The motor we had ordered is 175lbs.
The max outboard weight for this Mark 2C is 154lb (70kg).
So, I'm wondering, what do you recommend as a motor for this boat? We're buying Mercury, as that's what our small-town dealer stocks.
They have a 20HP, 15HP and 9.9HP. The weight of each is fine for the boat.
We'll be operating on a large-ish river (in good weather), and on lakes.
Thanks everyone, for the advice. Much appreciated.
ALSO: Checked the seams, looks fine.