I have seen this done to take advantage of the exchange rate.
there are a few pitfalls, especially if the hull already has a convoluted title through the NVDC
However, If you take posessions in international waters, and take the boat back to the US, you absolutely must have with you fully signed and detailed transaction documents and bills of sale that exactly match the names and IDs of the boat at each point in its past. Any slight difference in the history of the boat can make getting current US Coast guard registration a tedious process.
customs/Homeland security can provide you with the necessary forms required on bringing the vessel in, but I have seen that is much easier than getting corrected docs through the NVDC.
One of the things that will be difficult to document is the previous history. The us NVDC will have record if the boat started as a US vessel, however if it was exported to a dealer in Canada..........who knows. I saw an american built boat, originally documented, expired, sold to canada, expired, registered in province, Canadian national registration reapplied for, and through all this and errors in the Hull ID and first two vessel owners name. Then came the difficulty of deregistering a boat when you are not a canadian, it seems only the previous owner can do that in canada. (another stumbling block) and of course we cannot have registration current in 2 countries now could we????
When it came time to re-import that boat back from canada..... well it can be fun.
IT can be a trying process. IF it was not for the professionalism and can do attiide of the NVDC, that boat would probably be still sitting in Western Canada..
Talk with the current owners, Get copies of all current documents, if not current at this time, make the registration current before the sale. Dont skip steps. Dont let anyone die during the process.
have fun.