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.