I ran across this link that answers many questions:
Thoosa electric inboard frequently asked questions Australia
Amongst other things the recharge mode only costs you about .02knots.
On a 27ft mono hull he can push it a 4knot for 6hrs on a 215Ah battery pack. It also mentions using a 2kw generator. It never occurred to me that you do not have to run a 9Kw motor at the full 9Kw, reducing the Kw just means you go slower.