While good advice, this isn't really practical, if you are still using your boat actively.
That's a fair point. But put the "stuff" that doesn't convey into one or more of your bins and make it clear that that stuff doesn't convey.
To prevent this issue, I think the contract should read that nothing but the following is included.
If you are the seller and are presenting the contract to the buyer, this is a fine place to start. But whey you go to buy your next boat, is that really the position you want your seller to take?
In the end, a good contract will list all of the "stuff" that will or won't convey. The goal is to ensure that both parties' intent is properly memorialized, and that both parties have reasonably expectations when the money changes hands. In this case, assuming the OP is telling the truth about the language in the contract, it seems to me that the "catch-all" provision (which is a smart thing to have in there) would benefit him.
I'd be very curious what other items were removed by the seller that weren't on the list. The seller of our first boat told me that everything that I saw went with the boat. When I arrived, the inlatable towable ring that was in the cabin (and that I had been creating lots of fun scenarios with in my mind) was gone, as were a few other things. Even when they said it, I wasn't so sure they really meant to include the inflatable in the "everything" description, so I just left it alone. They took a few other things off the boat, too, but nothing that was of any real consequence to me, especially at the price I paid. If the seller in the OP's case took off good/valuable things but they aren't things he wanted (e.g., plates and silverware, glasses/cups, decorations, etc.) then I'd probably just let it go. But if any fixtures (lights, fans, equipment, sail covers, extra sails, etc.) or safety equipment (e.g., flares, minimum number of life vests, etc.) were taken, at a minimum I'd be a bit peeved. If it was something REALLY valuable, I'd be tempted to call the police because there was fraud, and possibly theft, involved. But, actually, as James said, if I really felt like something fishy was happening, I would have canceled the transaction, stopped payment on the check, and walked away.