Good morning, all,
Lots of info on this thread- some good, and some not so good.
The bottom line for all policies is not price or discounts- it's coverage. Most (if not all) homeowners' policies do not cover specific marine related incidents such as pollution, salvage, wreck removal, environmental disasters, and more.
For the record, I am redneck joe's "guy". Specifically, our company is a marine specific (and only) brokerage- we do all types of maritime coverages including private pleasure, charter, commercial, marinas, docks/wharves/piers, overland transit, ocean cargo, marine artisan, builders' risk, and more. We are licensed in all states, and have offices in Florida, Alaska, and Seattle.
Agreed Value coverage is preferable to Actual Cash Value coverage, The major difference is simple- the Agreed Value policy determines the vessel value at policy inception, and the Actual Cash Value policy determines the value at time of loss. There are quite a few other differences, but this is the major one.
Next, it is a fools' errand to just add your boat to your homeowner's policy. The yacht form is written based on admiralty law, and defines specific marine incidents and perils. Many companies that specialize in auto coverage, with a sideline in covering watercraft, simply modify the language of an automotive policy (remove "car/auto" add "boat/watercraft" in the policy wording) without also modifying the rest of the policy to properly cover marine accidents.
As boaters ourselves (we are full time liveaboards on a 52' yachtfisher) we understand how the very word "boat" can make things more expensive. At the same time, all of us as boat owners have real money invested in our passion- not the mention the required maintenance, fuel costs, equipment, etc. Time and time again, our company has advised clients on the above issues, and there has been quite a few times where the insured had a claim, and the lower cost policy they selected ended up costing them thousands out of pocket- all because they didn't take the time to read their policy, and chose the lowest price possible over anything else.
Finally, make sure your agent/broker is working for your best interests- he/she should know what they are representing, and should be able to pretty much quote chapter and verse on the policy they are selling you, and have the policy language ready to send you for review.