As far as I know, CA luxury tax is based on value, so it's probably not that much for an old boat like that. Especially when you set the value when you buy it at $500. Who knows.
I do know one thing. AZ doubled their rates within the past year. My new boat reg just went up to $345 for about a 16 month period. My 1994 21 footer was running me $16 a year. The lady wouldn't take any excuses and said sorry, we doubled our rates !