MikeB4:
You should follow the example of the Wellington harbour ferry and go electric π Charge points off shore could be a problem though and extension cords are a bugger in water.
I did actually do some desktop work on that. A typical day's boating has me covering around 50 miles at around 25 mph (minimum tolerable speed in a moderate sea). Basically there is no way to achieve that electrically and still have a boat that floats. The there is the cost and the fact the boat isn't designed to handle the weights for even a 25 mile range. Plate deformation, 'push through' of the internal structure and eventually water ingress would result. A fundamental problem with e-boats, is that there is on mechanisms for energy recovery during deceleration and deceleration is infrequent.
A design that does work is a catamaran with long narrow hulls (low wetted surface drag and low prismatic drag) in an application with light loads. That's exactly what the new ExW electric ferry is. 135 people (~10,000kg) on a vessel that size is a relatively small load. It's a great design for the application but trying to replicate it within the footprint of a trailer boat would be very difficult.
The other design I have seen working is a foiling design which dramatically reduces wetted surface areas and prismatic drag. I've yet to see footage of one of these boats foiling in any sort of sea state. Getting a 6m boat onto its foils in 1m waves would be interesting, let alone keeping it there. They strike me as a billionaires toy with no application outside of sheltered waters.
I'm currently working with an outboard canoe design for a beach launchable boat for short trips in remote areas. Basically tow a lightweight craft to a fishy location with no boat ramp nearby and launch there. It looks like the electric option is twice the mass and twice the price of the petrol.
Another possibility is a adapting an ebike powertrain to work with a pedal-drive for a kayak - like Hobie's mirage drive or Old Town's PDL.