...Then buy a cheap generator to charge the batteries or maintain power once the batteries are dead. If you have an on board generator, that allows you to run other stuff too, like a small AC unit. There is space to stash a small generator next to the motor well, so one would not have to hear it or see it.
Seems like we all end up at the same place eventually. I went down this road about 10 years ago. I got a trolling motor for my boat and then went looking for a generator. The trolling motor was a good deal for $600 I had a 55lb thrust motor, battery AND the battery charger that came with the motor. And a small trickle charger for $20 on eBay was enough to charge the battery over a week... so long as I only sailed on weekends it was perfect. I could push my boat at hull speed at 3/4 throttle and it would last several hours before it started to die off. It was fine so long as I only sailed weekends and only used the motor to get back to port when the wind died.
Then I started thinking about longer trips and the desire for a generator came to mind. I think I even posted here with a few questions.
To get a generator that is silent enough and small enough to be practical you are going to spend some money. Honda makes a really nice one. And now you have a gas powered device that needs a fuel tank etc.
Add up the trolling motor, solar cells, battery and generator ... you could have purchased a nice 6 hp Tohatsu with a 6A alternator already installed. A lot more thrust and it is much quicker to fill up the gas tank than it is to charge a dead battery. Also on a 10 gal tank of gas, you can run the Tohatsu all day. On a battery you are only going to get a few hours out of a trolling motor at 3/4 throttle.
I think if I ever get the desire to go down this road again (someone please kick me) I think I'd spend the money on bigger solar panels instead of a generator. Solar panels are 40% cheaper than they were 10 years ago. But honestly, if you want dependable power to spare, and the ability to charge the house battery, get the Tohatsu 6hp sail pro.