The loan can vary - Most quotes I've seen from Moorings are 15 years. But you can come up with other financing options as well. With their options, their payment to you over the 5 years is equal or greater than your mortgage payment. IF you want to see real numbers, reach out and get a quote on a boat you are interested in.

Only using 10 days a year though, it may not be worth it, but that's really a personal decision. If having a good portion of the boat paid off by charter use is what you want, then it could benefit you still. You'd just want to sell as much time as you can (maybe see if you can negotiate more) and put that towards the mortgage..