-- Would you let them take the boat out sailing if they had sufficient experience? What about if you wanted to take the boat out for a day or weekend, is that a faux pas?
Not exactly the same thing but my friend has a boat he lives on during the summer. When he goes on vacation the boat is mine. I take it out day-sailing. Of course I fuss over the boat a lot more than he does so he doesn't worry. And of course I'm the one that is usually sailing with him when he is here.
This is such an individual arrangement I depends on the people involved.
One trick you could borrow from the charter people is to hold a deposit equal to the deductible of the insurance.