Re: boat insurance
every motor boater should have liability coverage, and throw in uninsured/underinsured coverage as well. It does not matter how, where or what you boat in. Not less that $200,000
Liability will usually include med pay and similar coverages.
Property coverage (meaning coverage of YOUR boat if something happens like it sinks or you crash it) depends on the value of the boat; many companies won't cover old ones but at the same time, many will throw in property when you buy liability. As for value, there are agreed value policies, which protect you from the vagaries of valuing a used boat, which will always be less that you think its worth and not enough to replace it.
I think it's a good idea for most people to get an umbrella policy, and if so, your underlying liability coverage has to be high enough to reach the umbrella.
Look at your boat and auto coverage to determine what happens if you are in a wreck while trailering your boat--is your liability covered and is your boat covered.