I lived on a mooring in western australia
and had this same problem.
Unfortunately, our mooring field was renowned for poor mooring maintenence, and every season, without fail, several boats would end up on the beach in a storm.
Unfortunately, one season, a larger boat blew off its mooring, and crashed into the bulk handling warf - the insurance
company was also liable for the repair and lost
production while the reapairs and salvage
were completed to the warf. Much more than the value of the boat.
My insurer cancelled my insurance soon after, and probably insurance of several other vessells in the area.
I ended up going to an insurance broker, who shopped around for me. Eventually, he found me a deal.