As a buyer looking at boat listings, you should reasonably assume the listing broker is an agent of the seller until you discover otherwise.
I would figure that this is self-evident.
And, again, this is not necessarily a bad thing.
A broker's job is 1. sell the boat. 2. Sell the boat for the highest dollar possible.
An effective broker will not focus on 2. to the detriment of 1.
Not all brokers are great, but the majority aren't wastrels, scam artists, thieves, grifters or general ne'er do wells.
Otherwise the profession would be much more tightly regulated...
like the legal profession.
(c'mon, I couldn't help it.
I posit that the vast majority of brokered sales are satisfactory and hassle free. Few folks ever start a thread to give an attaboy to a broker who did his/her job well.
However, many folks will happily and loudly complain when the wheels fall off a deal, even if they are at fault, partially or completely, and, with relish, tear a strip off a broker. On every forum. Repeatedly.