you have such great suggestions, but the reality is that there are too many unknowns starting from the wishes of the gifter, their relationship, this contractual agreement, etc.
Honestly, from everything I'm reading, this seems like a great gift for someone looking for such a gift, but for you it seems to be an even bigger burden. It's 'only' worth around $100k assuming it's in really good condition, so I don't know why you'd want these headaches. The amount of money
you may sink into it's upkeep/storage for 3-years you may not even be able to recoup when you sell the boat.
I would go to a broker and find out the true value of the boat, what people actually pay for it. Figure out what your TCO will be and subtract one from the other (figure in for slight depreciation and interest) and you'll have the total value of your 'investment.' I bet by the time you're done doing all the math you'll figure it's easier to politely refuse the gift stating you can't afford the vessel rather than taking something you really can't afford to keep.
a boat were the end of it, I'd have my dream yacht sitting at the docks right now.
Just my humble opinion based on all the information I've read in this thread.