What do you think? Should I still trust this guy after a stunt like that?
Telling him to take a hike would be satisfying, but may not be in your best long term interests.
I would politely point out to him that he had agreed to have you do the work and that based on that agreement, you had arranged space and crew to do the work. Tell him that if he doesn't want you to do the work as agreed, then you can renegotiate for the work that he does want you to do. Hand him a bill for any real costs you have incurred up to this point.
Then find out what he wants you to do. Give him a written estimate. Once the two of you reach an agreement as to the scope of the work to be done and the price, then have him sign a contract. Do this all very politely. He will get the message that you no longer trust his word but need his signature on a legally binding contract.
The advantage of this, is that you likely will still get some work. You also stand a good chance of impressing upon him your own professionalism, and if you do a good job for him, that may result in referrals. If he realizes he screwed up, but you handle it well, he is likely to appreciate it. He may become a good long term customer. If you tell him to take a hike, he will just tend to blame it on you and you'll have someone in the area telling other boat owners about his "bad" experience with you.
It is too bad. I verbally agreed to have two guys that came recommended commission my recently bought boat for me. We didn't know each other, but knew of each other. They did the work as agreed. I paid them as agreed. Very simple. I just paid a guy to buff and wax my boat while in the water. I got his name from a recommendation. I called him, we agreed on the work, he did it and left an invoice in the companionway of the boat, and I sent him a check. We spoke on the phone 3 times. All very simple and easy. It is much nicer when business can be conducted on the basis of trust and performance.