Moe, not a military person, but thought there was a M 60 tank. Guess too much History Channel.
Mbouldin, no idea what the Cub Cadet you are talking about is like, but I have had and used a few mowers with Kohler engines. They have always held a load very well. No idea how their torque compares but that would be my choice, one reason, many more mechanics here and parts for the Kohler.
I realize there are many dam designs but I would look very carefully at a mower to use around a pond. You need a cutting deck that extends a good bit past the wheels or depending on the dam itself one to cut the sides of it. Have played with this idea a lot and maybe the lowest cost was a self powered pull unit such as DR or Swisher sells. I found two problems for me, one was the angle of my sloops were greater than the engines were safe for lubrication and the other was they had wheels past cutter width, limiting it. No idea how this may vary between the two engines you mentioned but suspect either will handle all the angle or sloop a ride on mower will.