Just stumbled across this and can help a little.
Bess and I have been to Jamaica several dozen times and have seen nearly every corner of that amazing island. Even done some boating there. Obviously, we love it there.
BUT... would I boat there full-time? Probably not. The island doesnít really have the infrastructure for boating. There are only three or four marina on the entire island and practically zero boating related stores... in fact, I canít name a single one. Boat repairs there are bodged together shade-tree fixes that may or may not last. Moreover, you will have to fly to Miami to get parts and smuggle them into the country. If customs nabs you, the duties are steep!
Now, if I had to pick a town, Port Antonio has, what we think, is the islandís only travel lift. And as you can imagine, it isnít in very good shape. But itís there and that is something. Port Antonio isnít what it used to be. What used to be the playground for the rich is now so far out of the way that few tourists (and their money) just donít get there very often. An option would be the Montego Bay Yacht Club... itís showing its age since it was fixed up for the Pineapple Cup, but a few rich Jamaican have their sport fish boats there and there are even a few live aboards.
Something else to consider is the island, for lack of a better way to put it, is kinda turned the wrong way. It runs east-west, and with the trades and current, is always a choppy trip. That may or may not be tooooo applicable to powerboats, but it is worth noting. Catch the right window and you would have a beautiful day.
Now, could you live there for six months and then back to the states, yea sure. But you need to make sure you are mechanically sound before you get there.
I would encourage you to go there and look around and talk to any boaters you find before you set sail. Things move pretty slow there. But that is a plus sometimes