Grunt is not a easy number of pounds of push or speed when heavily loaded or lightly loaded.

How deep & wide is the waterline ? A couple of pictures with the ruler along side would help.

My old Artasania 40" tug with 1 large, 6" x 2" Pittman servo motor on 12 v, with a 3 : 1 timing belt reduction, driving a Octura plastic 2 blade 2.8" x 5.0" prop can pull a Aluminium fishing boat in no wind.

Rich