HCANA requires a minimum $100,000 liabilty coverage to race.
Some homeowners policies allow riders for boats. Trailers may be in seperate from boats and/or a rider to an auto policy.
A $300,000 liability only policy would be roughly $45 per year. Of course then insure your boat and gear for your "replacement" value.
US Sailing one design policy info here
http://www.ussailing.org/odcc/boat%5Finsurance.htm 
