A year is not that long to be alone. Sure for some it would be and you wouldn't know if you like it until you tried it. I know I can so see no challange other than the money part. On a boat you will not be able to avoid people unless you bob about in the ocean in which case weather will likely end the experiment.
If you are wondering if you can handle isolation a boat is not needed.
You can even talk to people and be alone. Move away, do not make any friends, keep all conversations to a minumum, and see how you do. How long before you start to need those connections, how long before you have to reach for the internet, TV, or other media to feel connected. You can even find a job that has little interaction. Some people love it, others not so much.
IF you think it isn't a challenge then do it.. You can still talk to people, you just can't have people aboard the boat with you.. the challenge is being confined to one area for a year.. true you don't need a boat.. you could confine yourself to a house as well.. a boat just makes it more interesting.. if you can't see the challenge of not leaving a small space for a year I don't know what to tell ya.. But I bet you couldn't do it.. I don't even know if I could, but I'd love to try and see..