Personal opinion from a region with a lot of brokers and a lot of boats, typed as fast as I can.
A good broker is local and been in business a while (20 years would be nice). He is often in the office because he manages the joint or owns it.
He knows who the seller is, because he doesn't sell boats owned by known flakes, or boats with giant problems, because he has been in business too long for that hassle. He can and will get the seller on the phone and ask him your questions. He isn't an expert on the boat on, nor claim to be, but he knows a lot about boats. He has a reputation. He has survived in what is a difficult business that depends on reputation, and weathers deep recessions periodically.
He probably won't list many boats for an ask of less than $30K, because private sales make sense for that. He probably takes 10 percent of the sale price. He proably has a minimum, maybe 2K, meaning that if a $25K listing sells for $15K, he still gets 2K. Broker quote: "I have to have a minimum or else the sales people won't show the boat. It will just sit there." More on salesmen in a moment.
To sell a boat, I visit the owner or manager. We work out a plan for the photos, specs and such. We look at the broker's proprietary report on actual sale prices of my model nationally and locally--a list not available to private parties. We price it together. Usually "high." Broker quote: "People want a good deal and that never means paying more than the asking price." The broker is a partner in the sale, and I plan to rely on him to get it done.
The boat will actually be shown to prospective buyers by a salesperson. They usually know something, but rarely a lot. They are not in the job as a career. They get a commission when they sell a boat, often split with others who have shown it. The good ones offer to follow up with the owner on specific questions, but often don;t. They usually never see a prospect again, and showing boats to strangers isn't much fun, I am told. Deals fall apart, emotions get crazy over a missing dinghy oar. One deal I had, that fell through at the last moment when the boat was withdrawn from the market, the salesman/broker confessed he had shown the boat 17 times and now would never get a commission at all.
The reality is that Ericson owners and buyers are in every case dealing with a product that's 30-40 years old or more. Brokers weren't designed for that--the money is in financing a new Beneteau with 20 percent down. Old boats aren't eligible for bank loans, so all Ericson owners must have other financial resources. There's much less opportunity for an impulse sale. It's just harder. Folks are afraid of being cheated. Cheated? No old boat has a set value, it's what somebody wants to pay.
So, in sum-- and to get back to the Rams vs Seattle Wild Card--brokers are invaluable for boats over 30K, and have marginal commitment to small or bargain boats. Their interest and commitment will show accordingly.
This is LA, of course: 5,000 boats in Marina del Rey, 18 operating marinas, sailmakers and support business all around, reputations easy to discover. May not apply to more pastoral zones, or a zone with a viable quarterback in post season.