I have been an insurance broker since 1988 but do not do boats. But I do know that in general an error of omission on your part could be a material misrepresentation and could come back to bite you. If you are cruising beyond the local area that the policy covers and you come to grief outside that area you would not have coverage anyway as every policy has navigational limits that are clearly declared. You might consider working with a broker who specializes in yacht coverage, telling him the truth and letting him search the market. By putting your cards on the table the broker will find a carrier that would be agreeable to cruising as opposed to one that might be cheaper for local coverage but would say no to cruising.