Not sure if this is something that would work in Washington state but we have something of a loop hole in Idaho for drift boat trailers. We simply call them utility trailers and can get a 10 year sticker for like 20 dollars. On larger boats, we also have an good program. You can pick the county your money goes to when you renew your sticker every year. That way, the money you pay goes to the county that you fish in most often, for ramp improvement etc. In many cases, the countys that see the most fishing days are rurel, with low tax base. This helps a lot. Instead of the money going to the state which is really just a black hole..

One more good deal... Drift boats don't need stickers etc. They are concidered white water craft just like a raft etc.