[diesel-electric small-boat propulsion...]

This is an interesting idea, when under sail the prop spins and recharges the batteries - I would imagine there would be a certain amount of drag, - but with one a few solar panels I would think you could go a long way with this system.

http://www.propulsionmarine.com/electric

[RIBs What is the best brand now??]

Anyone seen or had anything to do with these - Not sure how tough the floor would be but it would Pack up a treat. http://www.promarinesh.com/AH.html