I used to work with eBay Motors for their fraud protection programs. One thing we used to help cover people for is recieving a vehicle (including boats) without a title, if the vehicle came from a state which required a title.
That being said, I have a lot of experiance in obtaining titles to various kinds of vehicles. Generally, so long as the vehicle is not stolen, or does not have some kind of undisclosed brand on the title which prevents issuing a new title (for example that it was "salvaged" or "flooded") you can almost always obtain some kind of title to it in nearly every state.
While you may be able to get a title, that doesn't mean it will be easy. I don't know about S.C. specifically off the top of my head, and it sounds like some of the other posters have experience, so I would listen to them.
Standards vary widely from state to state, especially when it comes to boats. The one thing that ALL states have in common, however, is that dealing with the DMV (or whatever beurocracy is responsible for boats) is a generally horrendous, gut-wrenching experiance.
I guess all of this is to say, if you live in a state that requires a title (not just registration) for a boat, and if you value your time, don't by a boat without the proper paperwork. If, on the other hand, you enjoy endless hours on hold, waiting to speak to a total idiot at the DMV, proceed with the purchase.
