Is looks like $40 for initial and $30 for renewal?
http://www.dnr.sc.gov/boating/fees.html
http://www.dnr.sc.gov/boating/forms/pdf/Application.pdf
Maybe I'm wrong and there's an annual luxury tax? There seems to be a 5% tax on purchase, capped at $300 max.
This interests me as my long term plan is to relocate to SC. Unless the tax was crazy high on boat or other vehicle annual registration it would certainly be cheaper than living in NJ, which I believe has pretty much the highest taxes and cost of living of anywhere.