Not an attorney, but it seems to me that if he had damage to his property caused by your boat he should collect for those damages from his homeowners policy (minus the deductible), and that company should go after your boat insurance policy. That's why both he, and you, pay insurance premiums.
The insurance companies might play games, but in the end they have to pay if you both had valid policies. If I were you I wouldn't talk to, or deal with any insurance company but your own.
I was in a similar position a few years ago as the homeowner where your boat landed.
A parked car popped out of gear, rolled down a hill, and hit my house back in 2005. Huge PIA, but my homeowners company paid for the damage to my house minus my deductible. A year or so later when they settled with the company that insured the car I got a check from them for my deductible. The amount they got from the company that insured the car was not my concern. From what I understand, the first dollar they collected had to come back to me according to the law, and they got whatever else they collected after I got my deductible. I guess it works that way because insurance companies often negotiate back and forth.
If the property owner in your situation didn't have homeowner's insurance, or is just stupid and doesn't want to go through his company, then he can put in a claim with your insurance company, but he will get lot's of aggravation and learn that it's always best to have your own insurance and use it when the time comes.
He might be reluctant to put in a claim with his company because he lives on the water, pays high rates, and doesn't want them to jump anymore. But as I learned when the car hit the house, as long as you have no fault at all in the incident and your homeowner's policy can go after someone else, your rates don't go up.
His company might also be able to go after the boat yard's policy depending on the circumstances. Your boat insurance company might be able to go after them too.
The real fight should be between your boat insurance company, and the company that insures the boat yard. Either way though, your company should be taking care of you and fighting it out with you.
As far as the bank is concerned. If they are the lien holder on the boat, then they will get whatever check comes from your boat insurance company for damages because they are technically the actual owner of the boat. If the amount of the insurance check were to exceed what you owe on the boat, then you should get whatever that excess amount is. If that amount is less than you owe on the boat, you are still responsible for the outstanding amount.
If the yard that is trying to bill you has possession of the boat, they will probably seek a mechanics lien, if they haven't already done so, on it. If they get that lien, the boat is theirs. The bank will still want their money from you though.
If the yard that is billing you for the work you didn't authorize puts a mechanic's lien on the boat for unpaid repairs/services/storage, then that opens a real can of worms. That's the main thing I would try to fight with a lawyer if I could.