I finally just settled for liability insurance with an umbrella.
A couple brokers wanted pics of the boat and the engines before quoting. Others asked if it was over 100MPH. Any two of the aforementioned criteria was enough to kill the insurance. I did have one quote for over 12k a year through Lloyd's.
So my comprehension portion is self insured. I screw it up I pay for it!
Sy was great. he gave me every lead he could imagine. The 12k/yr quote was derived from his leads.