You can run, but you can't hide.
A Canadian bringing a newly acquired possession home will be subject to the duties and taxes levied for that particular item upon entry to Canada.
For boats there is a time limited exception, if you come in for a refit. It doesn't have to be much, I think some have done as little as restock the fridge. Last I checked, it was 90 days, but could be extended.
If you are considering buying a boat in Seattle, check the prices here in Vancouver too. I think you will see a difference that makes it cheaper to buy in Seattle and pay the man to bring it home. $Can is over $.92US right now, so timing is good.
I kept a boat in Point Roberts for 2 years and found the border crossing to be a hassle. That was before 911, so things have only gotten worse. If you want to use your boat every weekend that could be a factor.
There are lots of US registered boats in Canadian marinas. That doesn't mean Canadians are able to avoid duties and taxes. Check with the owners and you will find a US citizen involved. We can do the reverse and keep a Canadian registered boat in the States. PR
Marina exists for that market.
Good luck in your search!