registration of US purchase by Canadian
If the boat is documented by the US Coast Guard, I would say you should contact them. Do a web search on US Coast Guard Vessel Documentation Center. They have an 800 number and they were the most helpful people I ever dealt with in government.
Registering a boat off-shore has tax advantages if you are buying a mega-yacht. Otherwise I would guess there is headache involved.
If the boat is not documented but the title is a Florida State title, I would still check on documentation requirements. You really need Federal Documentation to go to the Bahamas, etc.