I was looking into an electric for my boat awhile ago. I don't have a lot of faith in my current diesel but I tabled the plans as I don't have a place to put the batteries or a generator to keep a smaller bank charged up to what I wanted to be able to motor. This is what I was looking at:
5 KW Inboard Oddysey makes some rack mounted batteries in a form that would have been workable for me but the cost was too much. So I am sticking with the diesel until it dies.
There is a guy here in the marina with a pretty big Gulfstar and he put a forklift motor in it and it is working ok. He needs to get a new prop as he found out the motor does have a prefered direction it wants to rotate and he has to put the engine in reverse to go forward. he said it does back up quite well though.
You may have issues charging a 48v bank with wind or solar though. 12v seems to be the predominant output of the units so you would need a clever charge controller that may not exist to step up the voltage to charge level or run panels in a group of 4 to get the voltage up. I did not get very far into it before deciding it would not work as well as I had hoped.