Re: Optimal propulsion system
Silly idea perhaps, but what about an outboard motor on a bracket? Ugly perhaps, but not overly expensive in comparison. The 4 stroke ones are pretty amazingly quiet. Could use that most of the time, then fire up the big diesel if you really needed the power. That would probably be the most economical and simplest solution.
FWIW I think electric is a great idea overall, the power generation potential while under sail would seem to me to be a nice bonus too. The costs certainly aren't insignificant though, especially if you want to be able to move at hull speed for as long as you have fuel. If my Yanmar dies I may got that route.
It's the last idea that I don't really understand perhaps. What is your current fuel range at hull speed? If you could have enough batteries for even 50% of that range, and a generator that could charge your batteries at 50% of the consumption rate(5kw for example) you could get the same range as your current setup if needed, much easier than trying to have a generator that will produce 100% of the electric motor's requirements. Or 75% of the range on batteries at hull speed, with a generator that could produce 25% of your requirements... Which would get you almost to the Honda 2000 territory.