Notwithstanding the problems with Re-e-power's business practices, I don't understand why using the original prop and shaft isn't done more often. It's already there, is in the proper place per design, and makes a lot more sense to me than hanging an expensive electric motor in the water where it can have issues. Not to mention the drag. Here's a link to a photo series of a guy who repowered his Newport 28 with electric. E-POD 3000+ - Petaris' Photos
If you go to the last series of pics you'll see the problems he had.