Scott, I worked on re-doing a Dumas Pay 'N Pak style hull in the fall to get it going for someone. While you could do electic, I think the hull is a bit to large and heavy to use the commonly available electic powerplants and electronic speed controls (like from the UL1).
Most of those old style Dumas 3 point hydros used a K&B .45 inboard marine engine. You should be able to find one on e-bay in the $75-$100 range. I would try to get one that has an RC carb instead of a venturi and exhaust throttle. Using the RC carb is easier to use on a 'sport use' hydro.
The other 'big' thing you will need, if you do not have one, is a radio system that has the transmitter, receiver, and two servos (one for steering...one for throttle). Your local hobby shop should have entry level pistol style radio systems that start around $50. Some of the newer radio systems use cellphone tecnology (no crystals) on 2.4 megahertz and cost a bit more but are far superior to the older style crystal type systems. They start around $80.
The boat I worked on needed to have a new driveshaft and the original turnfin replaced as the original ones were inadequate. It would help if you could take some pictures (top, bottom, rear, etc) and post them so we could see what you have and the condition. RC
