The good news is that the maximum sales tax in SC is $300.00. However, if you leave it in SC, they will hit you with Personal Property tax on the boat regardless of whether you have a shoreside address in SC. The amount and timing is assessed county by county.
Every state has its hand out looking for your money
. And they will get it. So make sure that you know the rules in your state of residence and where you keep the boat. Documenting the boat usually will not help you hide from the state revenue folks depending on where you live/keep the boat.
When we bought Painkiller 2 yrs ago, I made the purchase in MD and the broker was from FL. I had to sign forms from both states saying I was not keeping the boat in their jurisdiction, or else they would assess the appropriate taxes
Do a search on the archives
here. There has been lots of discussion on this topic.