rusty, your best bet is to go to the State of Florida Dept. of Reveneue web site, http://www.dor.myflorida.com
and check out their exact regulations online.
One of many useful pubs they have available online.
Generally, if you are from ot of state and you are getting the boat out of state within 90 days (no
excuses for 91 days) you won't owe sales or use tax on the boat, and there's no nonsense like taking delivery three miles out at sea. If a boat is within Florida waters for 90 days--they're going to want registration and taxes, with very few exceptions. Florida is full of "water cops" of varying kinds, all quite eager to writ summonses.
Follow the rules, sned them a written query if you have any doubts, and you should have no problems. And no need to make a sale on the high seas.