My last boat went to Indiana from here on Long Island.
Buyer paid me through wire transfer, then I Fedex overnighted to him the keys and CG Documentation (title), the very next morning after I saw the funds cleared in my account. Boat got hauled a few weeks later. No survey. I never met buyer.
I just bought a boat in NJ, paid deposit wire transfer to broker, bank is handling everything else and title company for tax and reggy. I had it surveyed. I will never meet seller.
My last example, I bought a Harley from New Hampshire distributor/reseller, did wire transfer, shipped bike a short time later, never met seller.
Bottom line is that you need to feel comfortable in the transaction. Just use a method of payment that is completely traceable. Paypal is ok for a deposit but no one will let you pay in full through paypal, they will whack him with a percentage that hurts. I believe 3%.
You can ask seller for info and notarized signature, etc to spell out the transaction with HIN and motor numbers and listing all bolt on options (electronics) with serial numbers if you like. He can snap a pic of title and email it to you to show you no lien listed, etc. Communication is important during these types of transactions. Someone always immediately reachable for each step will reduce anxiety. Ask him to overnight you title as soon as funds clear. It is not expensive and it is the right thing to do.
One thing that will not happen is a seller will never send you title without all funds in the bank and cleared. I would not do it and would not expect a seller to do so for me.