Engineers, both formal and backyard, along with serious bicycle racers/riders....
Does anyone have any experience or knowledge of a bicycle pedals and gear system being used to propel a sailboat?
I am sure there is a limit on prop size, displacement, etc. but it seems reasonable you could transfer that force to the drive shaft, then use the 15 speed gear system to get the prop spinning and boat moving progressively.
Possibly it could also be used to charge your batteries, when not propelling the boat.
Or possibly a stair climber type device....where your weight powers a geared system? Maybe more compact than a bicycle crank, pedals , gears, etc. You could use it at the companionway and have a way to lock the steps when not in use, and it would be close to the shaft location. Although you would need someone at the helm as you wouldn't be able to see where you are going.
I do things and think of things others consider crazy. Crazy to me, is spending 100 dollars a month to go to a gym, to move weights around, just to get exercise, when you can get your exercise for free, seeing the world around you.
I also strongly dislike the sound, smell, potential leak points, cost, and space taken up by an engine.
I am not talking about long distance.....although I don't rule that out if you enjoy that. Mostly just getting into a harbor when the wind dies or into tight areas.