Some of these are pretty expensive but have you looked at a bait boat style to haul a line? They use 12v batts for hours of run time, I don't think gas or glow would be reliable enough then how to you get it back if it dies? The ones with the wireless depth finders are sweet too but lots of $ but maybe you can get some ideas.
12v motors you might be able to salvage from a car wiper motor or the like. Batteries could come from scooters, electric wheelchairs, emergency lighting.
Most of them seem to have jet drive or at least shrouded props to prevent snagging the line.
You might be able to tell what kind of props they are using.
Best of luck catch a cuda for me.