Interesting. Thanks for the responses.
I am a resident of MA.
When I purchased my previous boat (also documented) I sailed her out of Rhode Island (was not even aware of the tax implications). However, we moved her to MA and sailed her out of Mattapoisett for three seasons. Nobody ever came after me for tax - and I wasn't aware I was dodging it. I even paid the local harbor tax...
Is there perhaps a time-frame that one owns a boat for after which if it's transferred to another state, tax is not liable?
It's not a big deal - we can certainly continue to moor in RI another year - we're headed off on a circumnavigation in 2013, so this shouldn't be an issue then!