I've been on five seatrials, both as buyer and seller - and none went exactly like the others. The first sea trial with surveyor present, I was the buyer and the surveyor worked for me. He was the boss-man in my mind, having decades more experience with these things than I, the reason why he gets the big bucks. Therefore, I followed his lead. Always use the seller's broker's advise with some level of suspicion.
I suggest you spend some time with your surveyor, well in advance of leaving the slip. Ask him what you should do to optimize the time away from dock - and he should give you some wise advice.
Even though we consider the sailing rig important, in my experience, the mechanics are most important and repairs to such could represent some huge dollar amounts.
As much as you'd want to stay at the helm - go down to the engine with the surveyor and watch him check engine temps with his digital thermometer, shaft alignment under load, potential leaks and any suspect and excessive vibrations. These could be signs of serious issues.
Then take the helm under power and sail, experience how well she tacks and gybes, potential issues with the furler and winches, and imagine yourself going through these motions without a crew to assist you.
After allowing the owner, or his broker, to dock the boat - step aside with your surveyor and talk about any potential issue he has with the boat . . . important to do this before he writes his report. He may suggest things that may otherwise go unmentioned.
Best of luck in your seatrial, hopeful positive negotiations and the closing process that follows.
True Blue . . .
sold the Nauticat