Forgetting about the boat and what it may or may not be worth, how about thinking about the energy required to move the vessel when wind is not what or where you want it, i.e 90% of the time.
Forms of energy:-
1. Heat energy, from the Sun or burning a chemical.
2. Chemical energy, from a chemical reaction between two elements such as carbon and oxygen which when catalyzed by spark or compression will ignite and convert to heat energy which when contained causes pressure.
3. Electrical energy which usually requires both of the above to make it happen.
4. MECHANICAL ENERGY which is what you really want to make that shaft rotate and the propellor to bite the water and push your boat along.
The mechanical energy required to push your boat along at hull speed for a given amount of time is a FIXED FIGURE and can be calculated in terms of horsepower, kilowatts, kilojoules, British thermal units or what ever.
So the viability or not of electric propulsion does not come to an opinion on the "green-ness" of it or any other opinion.
It is a scientific CALCULATION!!
The boat is designed with a certain amount of it's displacement in a certain location to be devoted to the means of propulsion and the fuel ie "STORED ENERGY" to power the means.
Therefore if the boat was designed to carry a weight of "X" being a combination of means of propulsion and fuel to carry it a distance of "Y" (anything less than 100 nm would be foolish), one needs to do the calculation to determine which method of propulsion come within the design factor of "X". Don't ask me to do the calculation because I know in my bones what the answer is.
One of the first laws of physics is that "Energy cannot be created or destroyed. It can only be changed from one form to another."
Simple analogy:- Compare an electric stove to a gas stove.
The electric stove requires CHEMICAL energy, converted to HEAT energy, converted to MECHANICAL energy, converted to ELECTRICAL energy then converted back to HEAT energy with losses all the way down the line.
The gas stove has CHEMICAL energy which you light to give you HEAT energy.
Have you got the picture yet??

Neuclear reactors have not been miniturised yet.