By all means, shop around, but before you pick a policy, be sure you read the policy--they're not all the same when it comes to what is covered and how they will depreciate your boat and gear when a claim comes due. I had an issue with my power boat insurance last year when I found out that they would not provide new parts for a motor more than 5 years old. As it turned out, I had paid for a higher coverage on my motor than they were willing to honor.
On the other hand, I had a lightning strike on my sailboat last year that was fully covered with new replacement equipment--but that was with a different underwriter. I had checked BOATUS a few years ago for a rate comparison, and I could have saved $200/year, but they would have depreciated the lightning-damaged electronics. I kept my original policy and am glad that I did.