Re: what to do
Look at if from the point of the buyer instead of the seller...
If I were buying (my .02), here's what would be acceptable to me:
1) Solid chance to look over the boat withou being rushed into price (in the driveway)
2) Hear it run on muffs until up to temperature, all while checking out lights, shift cables, electronics, etc. Allow him to bring a mechanic or other knowledgable person with him
3) Agree on a sale price, contingent on a successful sea trial. Good faith non-refundable deposit (could be as low as $100 to cover gas and time). This should be on a printed paper and signed by both parties. This is how dealers do it as well.
4) YOUR tow vehicle to the ramp. His vehicle may not have the proper requirements, ability, safety measures, or insurance to make sure the boat gets safely to the ramp and back. If it's his vehicle that gets used, would you trust him to launch/load your boat safely and properly?
5) Sea trial should really require no more than 10 minutes on the water, idling, at cruising speed, and at WOT. You run the boat. He may have never driven a boat in his life.
Your responsibilities include that the boat be in proper, safe working shape, look as good as possible, be safe to haul, have a reasonable amount of fuel in it, all required CG and registration requirements, and a clean title in hand.