A late response but I just did this. We bought a BC-built boat and imported it into Washington.
I called and spoke with the CBP folks in Pt Roberts, Anacortes, and Friday Harbor. All answers were slightly different! Here's what was pointed out to me:
1. The Pt Roberts folks are really a land crossing with no expertise or experience in vessel importation, only entry.
2. The Anacortes folks are experts at oil tankers and commercial fishing boats, so they reflexively state that a broker is needed.
3. The Friday Harbor folks are the most experienced in pleasure vessel importation, and have it down pat. Note that, while Roche Harbor is listed as one of the US ports of entry, you can't actually IMPORT the vessel there; it has to be Friday Harbor.
The CBP staff at Friday Harbor have developed a checklist and they emailed it to me. After much research, both in the US and in Canada, here's what I learned.
1. If you purchase the vessel in Canada, you'll be liable for sales tax. This is now called the "Harmonized Sales Tax" and is 12%, combining the old Provincial Sales Tax (7%) and the federal Goods and Services Tax (5%). The old Visitor Rebate Program went away in 2007, so you can't apply for a rebate.
2. If you purchase from a BC broker (a "PST Registrant"), they'll collect the tax.
3. If you purchase from a private party who is not a PST Registrant, it's up to you to voluntarily pay the tax. For BC residents, this 12% tax is collected by ICBC at the time the vehicle is insured & registered. For non-residents...well...you're not going to register or insure it in BC, so....
4. If you take delivery of the vessel OUTSIDE BC, you are not liable for the tax. However, you may not be aboard the vessel nor may you have a family member or friend do the delivery. It must be either professionally delivered or delivered by the seller.
5. Of course, you're going to pay Washington Use Tax when you register the vessel here. There is no way to avoid that. It varies by local jurisdiction, and will be something like 8-8.5% or so.
Now, it's a bit complicated if you purchase through a broker and have the boat professionally delivered to the USA. In that case, the CBP folks say that you MUST use a US broker at this end of the transaction.
But if you bring it in yourself FOR PERSONAL USE it's a very straightforward process, provided that you've done your homework. Here's what the Friday Harbor folks have put together as a checklist:
a. There is no cost for self-importation.
b. The owner should be aboard the vessel as it enters the US or at the dock awaiting its arrival.
c. You need Proof of Ownership showing a bona fide value. A Bill of Sale satisfies this requirement. I used the USCG Bill of Sale (form CG-1340). NOTE: this form has a box for "Consideration Received," which is sales price. But it also says "One dollar and other valuable consideration unless otherwise stated." YOU MUST STATE THE ACTUAL SALES PRICE.
d. You need the vessel's current license/registration in Canada. Note that vessels in Canada are not "titled" like we're used to, but are "licensed" in the province. This license, together with the previous bill of sale from whomever the owner bought the vessel from, forms the proof of ownership. Like our documentation, vessels may also be "registered" on the Canadian Registry of Vessels. If this is the case, you'll need the seller to provide you with a "Certificate of Deregistration" proving that the vessel has been removed from the registry before you can document it in the US. If you're not going to document it you don't need this certificate.
e. Evidence of origin is required, such as a Hull Identification Number, Certificate of Origin, Canadian federal registration documents, builder's statement, etc. They're not too uptight about this; our boat was only one of six or seven built by a guy 40 years ago, and had neither HIN nor any sort of original builder's certificates. We used the above documents plus a survey form that identified what the vessel was (i.e., built in BC) in order to establish that it would be covered under NAFTA.
f. Proof the vessel conforms to EPA standards. Our boat is 41 years old, so this was moot. If the vessel is older than 21 years OR if it originated in the US it doesn't need this. If the vessel is less than 21 years old and originally came from Canada, you'll need to read this:
https://www.epa.gov/importing-vehicles-and-engines/importing-canadian-vehicles. If it's older than 21 and was built outside of the US or Canada, you'll need to read this:
https://www.epa.gov/importing-vehicles-and-engines/publications-and-forms-importing-vehicles-and-engines. EPA form 3520-21 will be needed.
g. Bring along a completed form CBP 7501, "Entry Summary." This form is rather complicated because it's designed for commercial importers. Just download the instructions and follow them, box by box. If you're not sure of something, leave it blank and the CBP folks will fill it in for you.
h. Also bring a completed form CBP 1300, "Vessel Entrance or Clearance Statement." It's pretty straightforward, but they'll help you complete any blanks that you leave.
They're open seven days a week for processing entries, but they only do the importation process Monday through Friday. They request 48 hours' advance notice. I called several times as the day drew near so they were expecting us. Other folks were there in the office who hadn't followed the checklist to the letter and things were quite complicated for them. For us it was easy-peasy. Total cost of this process? ZERO. Of course, if your vessel comes with a dinghy or trailer, those require separate documentation in order to title them in Washington. Some other folks in the office did the transaction and only had to pay duty on the Japanese-built outboard motor on the dink.
We had an extremely positive experience with this process. The usual disclaimers apply: I am not a licensed broker nor do I have any sort of professional knowledge or experience with vessel importation; your mileage may vary. But the Friday Harbor CBP folks are really great to work with and genuinely interested in helping boaters out. They simply require that you follow some pretty simple instructions.