Cute idea, but physics makes it impractical, and expensive.
Li ion batteries weigh about 10#/kWh. The std 75 kWh battery will weigh around 750#, optional 99 kWh battery +-1000#. ...Petrol is 6#/gallon, these batteries cut into a 180 hp boat's max load capacity significantly.
6 kWh charger will...