I copied the question and answer below from the AGLCA mailing list. I think this exchange gives excellent information that many in the cruising community wil find useful.

My wife and I are hoping to buy a trawler early in the new year. One of the possible boats is located in Florida. Because we are not Florida residents and want to avoid the 90/183 day rule, it's been suggested to us that we do the closing in Georgia and remove the boat from Georgia shortly thereafter. 
Does anyone have information regarding Georgia Tax Regulations with regard to purchasing a boat in Georgia (but not as a Georgia resident)? 
John

John:
You can buy the boat in Florida as a non-resident from a resident.  You have 10 days to move it out of Florida, longer if bought from a dealer or broker.  That's what I did when we bought Georgia Peach in Florida.
In Georgia, if a Georgia resident buys a used boat (or car, for that matter) from another Georgia INDIVIDUAL, no sales tax is charged or due in Georgia.
Bear in mind, you will probably have to register, and probably pay applicable tax — ad valorem or sales or use taxes — in some state.
And don't confuse taxes with registration.  Different can o' worms.
Bill