I know your post is old, but I bought a boat in the US and brought it to Canada, so I'm not sure if the same applies, but under NAFTA, any boat manufactured in either country (even if built before NAFTA) is importable without a tariff, unlike, for instance a European boat. You will likely have to pay state taxes and submit forms/inspections as well as US Coast guard minimum safety gear which is slightly different from Canadian Coast Guard requirements.
"That's what a ship is, you know. It's not just a keel and hull and a deck and sails. That's what a ship needs. But what a ship is... is freedom." -- Captain Jack Sparrow