Could one use boat propeller to drive el generator?

[wackerb]

I've had two purpose built hydro generators I suggest you look at DuoGen, which also has a wind propeller which is not very efficient, but works at anchor. I had a lot of solar but cloudy days or shading by sails interfere with it. The other concern with an outboard type arrangement is hitting debris in the water. DuoGen just lifts up, but also has a "fusible" link so there is no damage.

I first had a SwiTec, outboard style vertical shaft which was nearly impossible to raise and lower under way and eventually the shaft broke off after hitting something. Plus, their support was abyssmal. I do not recommend it.

The water generation side of DuoGen got me across the Pacific and powered through the night running the autopilot and refrigerator at 6-7 kt. You have a prop and alternator optimized for the purpose. Saved me a lot of generator fuel. The only drawback was the controller which burned out but was easily replaced. I also added a cheap Amazon/china ammeter which bluetoothed to my phone. You need to keep an eye on it because seaweed will collect and disable it.