I just bought my first boat less than a month ago, so I can offer you some current info. I talked to a few different brokers. One of them was rather used-car-salesman-esque, I didn't like him. I eventually settled on one who was highly recommended both here on sailnet and by the author of a book I read. Everyone seems to say "find a broker you trust", and that's what I did. I discovered a number of clients that had used my broker multiple times, for both buying and selling. Every boat I saw, I saw through him. He never asked me to sign anything saying I was exclusively using him, nor did he mention it, but I got the distinct impression he expected me to not use other brokers. A good number of the boats I saw were his suggestions, but more than half were ones I found on yachtworld and expressed interest to him (including the one I bought). He'd then call the listing broker and get the inside scoop, and if that sounded good, set up a showing.
I have heard the commission is 10%, as SD said. I believe it is split equally, 5% to the listing broker, 5% to the selling broker. If the broker represents both the buyer and the seller, I believe he pockets all 10%. That situation nearly happened as I had an offer on a boat my broker had listed, but the deal fell through. I felt like he kept a good balance of the interests between me and his other customer (the seller). I told him the information he needed to know, and I consulted with him during the negotiations to get his reaction on how much I should raise my offer, but I was careful not to give him too much info that he might accidentally let slip to the sellers.
1979 Gulfstar 37 Laissez Faire