Re: Optimal propulsion system
I had been thinking about an electric option for my Pearson 30 for if/when the A4 dies. Electric motors are very efficient. With a timing belt reduction you have almost limitless combination for matching the ideal motor rpm to the ideal prop rpm. You will find numerous posts and articles expounding on the benefits of electric propulsion so I will not go into detail here. I will say that most of the claims are reasonable accurate. The one drawback (and it is a major one) is energy storage. Batteries are just not up to the task of replacing fossil fuels... yet.
The serial hybrid approach is one way to bridge the gap at this time. While not ideal it is, in my opinion, a good stop measure. As battery technology improves the only change you will have to make is replacing the batteries and possibly the charging system.
You will have to determine if electric propulsion will work for your mission in the first place based on your distance and speed requirements. For me as a lake sailor it is a good fit. When I was on the Chesapeake Bay; not so much.
The reduction in complexity and the very small size of an electric motor required to power my boat to hull speed was remarkable. The largest expense was batteries. Both financial and physical space/weight.
As I look at daysailer to replace my keelboat (new mission requirements) I am 90% set on electric for aux propulsion.