I had the pleasure of a tour of a rather nice electrically driven boat a while back, A submarine.
The whole of the bottom was batteries, 600V of lead-acids. Drive motor was huge.
Electric drive is the future, it will come, to boats as well as cars.
NiMH and Lithium batteries take space, but are relatively light. Charging
can be by the props when under sail, in addition to solar
. Taking power from the props cuts your speed down a bit of course, but it is free - when you have paid the high price
of installing all the motors and batteries. An auxilliary engine
to charge the bats is probably part of the equasion as well - It is just a generator.
Cost is the thing. And be careful about maintenance
, a 300V battery pack in a marine environment
is not a thing to be messing with,