You don't pay sales tax until you walk into the DMV to reg it. Then it's game-on. And, if they find out you have been sailing it, there's a little letter that goes to the state BOE. Then you're bummed. Don't get a ticket on an unregistered, un sales-tax paid boat, I know someone that got their boat taken. You'll see a line on your tax forms that says something like, "Mercandise bought tax free from out of state." That's the second place they'll get you if you don't reg it. Then they've got you for tax evasion. It's easy to get by that with small stuff, but boats are a different story.

So yes, if you import a boat and reg it here in CA, you pay sales tax.