If the boat is Canadian flagged and you do not intend to bring it back to Canada you will have no issue with Canadian taxes and tariffs. Just a change of ownership
with the Registrar of Shipping
As the boat is European built the note re not being offered for sale
in the US applies but can be circumvented as you're Canadian.
A cruising permit allows a foreign vessel to be in the US for one year. This would answer your initial question. How much time is left on the cruising permit?
I would think a change of ownership
if the boat is Canadian registered, and this is an important point, is easily done. Ask to see the registration
papers, used to be a "Bluebook" but now is a yellow piece of paper. Should have all details of the boat on it, official number etc.
The present cruising permit would apply if it's just a change of ownership. The change of ownership is all done in Canada and I would think the bit about being offered for sale
in the US would not apply.
Call the Registrar of Shipping
in your area and discuss it with him/her. You will get the proper info on what is required to change the ownership over to you. They will not be able to answer any questions regarding stay in the US.