-- Last Updated: Apr-17-06 7:43 PM EST --
I made a homemade bracket for my old town 158, and put a 35lb thrust motor on it, the bracket was a piece of 1.5" x 1.5" aluminum square tube, that spanned the gunnels just behind the rear seat, it stuck out the right side about 8", with another 6" piece bolted to the bottom of the right end (provides enough room to accept the motor mount pinch bolts). I used a 1.5" x .25" aluminum flat bar to go under the gunnels, and bolts/wing nuts to pinch the gunnels between the flat bar and tubing. (wanna pic ?) It would move along a bit too fast at full throttle (no gear but 2 passengers). The bracket hung off to the right side (reversible) and I had the battery in a battery box under the back seat. I could easily counterweight the engine by sitting to the left of the seat. It steered quite well, even in modest current, but I never checked to see how far I could go. I'd imagine that a standard deep cycle battery would last quite awhile at low speeds.
BTW...I can fab the bracket for ya if need be, cost of materials and shipping being the only cost. I'd need the measurement inside hull to inside hull just under the gunnels at the point where you want the mount to be.