There is no such thing in boating as a buyer's broker.
Only broker's paid by the seller, per a contract signed by the seller, all work for the seller.
That said, it's a good stategy to find a knowledgeable, personable broker that you are comfortable with, who will help you through the boat finding and purchase process, as if the best of buddies. Just keep in the back of your mind...the seller is paying him or her.
(If someone wants to object that buyer brokers abound...just upload the contract that proves it so...).
Certified...in several regards...