whirr...
It is unlike me to wade into a post like this with a reply but this one got the better of me.
A few things here seem so highly likely that they are worth mentioning as you think about this:
No matter how much you love the cruising, live aboard life, you will not finish you lifetime on a boat I am thinking.
In either a short or a long amount of time, the boat you buy will be worth less than you paid for it and will have consumed a lot of money in the meantime.
Meanwhile, because Seattle/Tacoma is largely populated by companies of the future rather than industries of the past, the economy here will remain very vibrant and keep pressure on real assets so the house you sold to buy the boat will be worth far more than you sold it for.
Unless you are swimming in other assets (which is none of my business and the reason I usually resist posts like this), selling your house to buy the boat seems like a disaster idea that does not end well.
If you hang onto the house and rent it for 3% of its value and it appreciates at 3%, you have covered the cost of a boat loan and still have someplace to live when you are done boating.
I will say from experience, that being a landlord is not for the faint of heart, but seems like it may be better than being homeless in Seattle when you are ready for the dirt house again.