| The fundamental problem is the physical limitations of the motor. If you have an electric motor that will push the HP to say 6 knots it will risk flying to pieces if left in the water at 15kts.

Are you saying there exists no electric motors that can push the 18m proa you are familiar with at both 6 and 15kts? Is pitch control not a thing?

|You also need to ensure the motor is happy to run backwards at speed as well when left in the water.

Given, as stated, one could swap the prop, why assume running backwards?

Are electric motors generally biased in rotation preference?

| In light to moderate wind, an electric motor just turning in the water will be a significant portion of the overall drag.

Sure, as expected. Are you saying there are lower drag and higher performing water driven power generation options? Or just clarifying, so that everybody knows, the obvious?

| Inevitably there is a narrow window of operation where you would bother to use the regeneration.

Sure. I have read many assertions that regen braking on electric cars is more a gimmick, and not worth it. Are you saying on boats its the same?
Or are you saying that if you need to put power in your batteries, because , for example, you need to motor along a canal in a few days, and it looks like the expected solar is not gonna do it, then you can sail at the regen point and charge your batteries?

| The significant secondary problem is range anxiety with any pure battery propulsion system. Regenerative charging is not of any use when your battery is flat and you want to make way through a channel in dead calm.

Stupid is as stupid does, right? I mean some number of hours/min/days before you found yourself needing to motor up a canal with a dead battery and a full electric system, if you had just turned on your brain, you could, I assert, not have your scenarios problem. Its exactly like any other time you run out of fuel, right?

| In fact solar panels are not much help either as you need to allow for the worst case charging, which can be close to zero for an entire day and the collected power may be just enough to keep the nav lights running and the GPS alive.

I mean sure. You can run out of hydrocarbons too, right?

And perhaps sailors need better skills managing power generation on electric boats?

But my point is, if, as one peers into ones immediate future, and the solar power generation is not looking to cut it, one engages the alternative power generation sources, like wind and pulling a prop, right?

Or are you saying there is no other viable alternative to hydrocarbons?

If, in your considerable opinion, spinning the drive motor is a crappy way to make power, that cannot be made worthy, then please say so. If it is only very difficult and tedious, but doable, then that's a different thing.

| The 18m proa has progressed...

Is that because the initial system engineering was weak? Or there just was not enough known about the domain? Or what?

Is it silly to suggest that the 52hp diesel might be way more efficient just driving a prop directly?