If the state you bought the boat in has notary laws similar to Ohio, as the buyer, you don't physically have to be there when the seller notarizes the title. The sellers signature/info is what's being notarized. Not yours.
If you've got possession of the boat and a way of proof that you have already paid the seller for the boat, you may just be able to call the seller and make arrangements to mail title to seller, let him get it notarized and Mail it back to you.