I've fiddled with figures and read some ideas and, at least for cruising sailors, believe electric is at a dead end.
That's because 1 HP = 748 watts (call it 750W/HP) So to generate 10 HP you would need 7500 watts or in a 12V system about 600 amps. Actually a little more.
Worked just fine for submarines, works for fork lifts (have you SEEN the battery chargers they use??!!), but I don't see a way to work it out on a boat that does not go home after a few hours of motor usage.
Seems like having an electric motor gives me all the disadvantages of having a diesel engine with a 1 gallon tank.
I don't think electric sailboats are going anywhere. And if I was the "King of Yanmar" I'd be making sure they don't by making sure sailors get what they need from me. Which is exactly what the current King (whoever he is) is doing.