Best advice that I can give is to check in here frequently and use the "View new posts since last visit" feature.
New boats show up in the for sale area frequently, so that method is your best method to see them as soon as they post.
I'm assuming that you have also searched Boat Trader and some of the larger online sources such as the Craigslist site mashup? http://www.jaxed.com/cgi-bin/sd.cgi
BTW - You don't have a location listed in your profile.
You might want to do that so folks looking to sell will know what coast you are on.