Let's look at the following boat: 2006 30' Baja 302 with twin 500's and a trailer

45 year old with clean MVR and boating experience.

Policy coverage quoted as follows for each state:

Hull and Machinery - Agreed Value $72,200
Deductible: 3% ($2,166)
Watercraft Liability: $300,000
Uninsured Boater: $300,000
Medical Payments: $5,000
Towing: $1,000
Trailer: $8,000
NO LAY UP - YEAR ROUND USE ANYWHERE IN THE US OR CANADA

Total Annual premium based on mooring state:
CA - $967.00

WA - $1047

TX (inland) - $1201

TX (coastal) - $1952

NC (inland) - $1070

NJ - $1172

WI - $881

Note the range of premiums from $881 - $1952 per year for the exact same boat, exact same operator, exact same coverages... know just imagine the rate changes when you factor in someone else's boat, age, engines, value etc...