Hi Doug and welcome,
You've got a number of options available to you, ranging from paper backed publications, to local newspapers, to the internet. The Boat Trader, Yacht Trader and Soundings are probably the most popular published classifieds, but in recent years, the numbers of pages in these books has steadily declined as buyers have turned to the internet.
The publications noted above also maintain a strong internet presence, with sites such as Trader Online, who also owns YachtWorld and Boats.com. Yachts, such as your Bertam, have historically been marketed through yacht brokers, but there is an interesting paradigm shift taking place, as consumers are turning to internet sites to sell their boats privately. There are many reasons for this, such as saving a brokers commission. The more profound reason seems to be how consumers are becoming "turned-off" by the high prices typically associated with brokerage boats. In recent years, the numbers of listings in YachtWorld have fallen as buyers are finding internet sites where they can work with private sellers directly.
There are a large number of websites specializing in boat listings, with about a half-dozen of them making into the internet mariner's reportoire. I'm not going to list the links. A Google search will reveal most of them for you. To start with, I would suggest placing a listing on YachtForums. A number of boats have sold through our website, because we are attracting a large number of yacht owners and people looking to purchase yachts. The best part... it's free.
Supplying high quality pictures of your boat will often be the difference in making your phone ring. Buyers will sometimes skip ads with poor pics, as this can be a subliminal reflection on the boat. Ofcourse, good pics can be misleading too. I can't tell you how many boats I've seen that looked good in pics and turned out to be rust-buckets in person. The opposite holds true too... poorly documented boats with lackluster pictures are sometimes sleepers.
With regard to fresh water use only - this is typically a strong selling point, but there are many more factors too, i.e., price, condition, hours, equipment, layout, proper maintenance, etc, etc. They all figure into the equation.