You have to list with the Aramark Boat Brokerage Service and pay them a commission. There are a few different options for listing your boat at different commission rates, but I think at minimum you have to pay a $300 administration fee plus 3% of the sale price. You can make arrangements on their website (http://www.lakepowellmarinas.com/boat-brokerage/brokerage-services/). The person to talk to is Brady Carothers; if you have trouble getting a response from the contact form on the website, I can probably dig up his phone and e-mail.
Looking back on my correspondence there is a less expensive option if you come to them with the sale in hand and just need to transfer ownership to the new owner; there are three options as outlined below:
1. The $300 administrative fee and 1% in commission if you handle the sale yourself and just transfer ownership to the new owner; for that you get no services from the brokerage.
2. The $300 transfer fee plus a 3% commission gets you an add on their Boattrader account, but they will do nothing else to sell your boat/shares other than pass leads on to you and potentially show the boat when potential buyers come down to view it (if it's on the slip/buoy).
3. The $300 transfer fee plus a 10% commission means they will act as more of a full service broker and handle the entire sale.
For me the extra 2% was worth it to have the Boattrader listing so that anyone looking for a boat under their brokerage would see mine too. Again, this is all based on conversations I had almost a year ago when I first looked at listing shares on my boat and may be out of date or mis-remembered; I'd suggest you just call the brokerage and discuss your options with them.