IMHO .... "reasonably priced" takes in account the profit margin of the dealership & what the dealership actually paid for the boat. Since they're not likely to tell you what they paid for the boat, offer them a couple thousand below what you think the boat is worth & see if they'll dicker with you. If the boat's been there for some time, they may ... but, if it hasn't been there for long, they'll likely try and hold at that price ... thinking someone will come along & pay that price.
Could be the boat is a trade-in or a consignment ... the asking price may differ on these two scenarios. But, to be sure, the dealer is gonna try and make the most profit it can on the deal, regardless.