I looked into this for Diana and concluded that electric propulsion is an overcomplicated mess for a small boat.
How will you charge the batteries? Like the Prius you still need a secondary system for charging; so in effect you need two engine systems on the boat. Why not just hook up a propeller to the charging engine that you need anyway and do away with the redundant electrical system? [brainstorm!
]
Consider the weight. The batteries are heavy; the propulsion motor, while not large, adds some weight; there is still a bronze prop, strut, and stuffing box; and then there's the generator/charger, its fuel tank and its (necessarily overlarge) alternator. And you're going to fit that into an already-cramped boat?
If you do
any regulat motoring at all, solar panels and wind turbines are
not enough to keep the propulsion motors' batteries topped-off, least of all the house bank(s). I looked into this and was told by one of the expert techs at Annapolis that 'it's not worth it' to install a wind fan. The guy literally told me to go get two 50-amp solar panels with which I'd have 'more than enough' power.
For me the real attraction is to be able to fit a sail-drive-type strut and prop so as to locate the propulsion system a little far aft and a little to one side as can fit best inside the boat. I even investigated the old OMC saildrive which was, in theory, very tidy and, in reality, a mechanical/maintenance nightmare. I am left with the original transom-mounted outboard setup which, while not elegant and not even very practical, is at least budget-friendly, simple mechanically, and easy to run, maintain and live with (1 qt/hr consumption + 12-gal tank = 48 hrs' straight running time, not counting 2-gal reserve. Beat that with any 25-ft sailboat!).
My best option would be a small diesel with which I can have a big alternator, cabin heat, hot water, and a clean transom, not to mention better fore-and-aft weight distribution. If you have this already, I envy you.