Yep, pics tell a lot. Standard gearbox with 9" 3 blade prop. It did well never the less, but you might want to think about the bargepusher (102 PLUS) as it has a much bigger but slower turning prop. Might give you a bit more thrust for manouvering rather than outright speed.
As you say, trying to mount a seagull onto the back of a barge isn't the best, but how else are you going to move it?
Good luck with fabricating a "manly" bracket for it.
Pics when your ready
Jon