Be honest with any buyers - If your boat has had a few bumps and scrapes in the past tell the buyer about them. He will be inspecting your boat and if he finds things that you have hidden it will create doubts in the buyers mind. If he has a survey done, they will be shown up anyway.

Tell them about all the extras - Most companies sell products by appealing to our desire for that little bit extra. When you sell your boat be sure to mention things that are included like radar, downriggers, fishfinder etc. My wife once bought a car because the front seats swiveled round so you could have a picnic, even though we only use this accessory about once a year. It could make a potential buyer choose your fantastic used boat over a shiny one in the dealer but with none of the fun bits.