My engine seized and it looks like I must either purchase a new or old
engine or simply replace the boat altogether (could probably only
afford a used one).

I am looking on the Net and find that there is much more options,
choices (and better prices!) in Washington State. I live in Canada
but near the Canada-US border so it would be easy to purchase
something in WA. But I don't know if there are legal, custom or other
issues if I purchase an American boat or engine (the engine I need to
replace is a OMC Cobra 4cyl 2.3L).

Andre