George,
Some good advice so far.
As common sense dictates, be fully aware that the sellers broker represents the seller and therefore, for all aspects of the deal, will (in theory) work to "sell" the boat. Your interest, needs, etc. are potentially not even on his/her radar!! Sometimes, it is very hard to get much info, help, or even get return phone calls from a listing broker.
However, as others have stated, there are a lot of "buyers brokers" who aren't adding much value to the deal, and maybe even just cause problems. If you decide that you will use a buyer's broker (I did and it worked very well for me), you need to spend some time researching several brokers. Ask for local recommendations, talk to other boaters for opinions, and go talk to them in their office, face to face. Prepare questions to help you determine how they (specifically) will work on your behalf, in your best interests, or would they "just want to get the commission". Some of this they will not answer directly, but you can often get a good feeling about it.
My buyer's broker did a lot of work for us, gathering information (especially when asked), showed us many boats (a few he just arranged visits for a first visit but did attend any we visited a second or more times). He gave valuable insight into the boat's condition, any specific info he had about that particular make/model, and after he really had a feel for what we were looking for, even told us a few times that he didn't think this one (we were then looking at) would be a good fit for us. He even freely gave advice and gathered information for us on a "potential deal" for us when the listing broker informed us he would not split commission. We did not have an explicit deal with our broker about this type of situation, so as far as he knew, he would not be paid, but he "worked" (without being directly involved) anyway. We did not buy that boat. When we did find the one, he travelled with us (3 hours away by car) for the viewing, then again for the survey and sea trial, where he again contributed valuable input. He recommended surveyors, documentation services, mechanics, etc. to help us complete the deal, and import the boat to Canada. Due to the fact that the boat was located in the US (LaConnor, Wa), on closing he drove us down to pick up the boat, so we didn't have to somehow arrange to get our vehicle home. When there, he drove us to various stores so we could provision (food, etc.), to West Marine for a couple of needed items, and to US Customs so we could obtain the needed "Cruising Permit" for bringing her home.
We felt that our broker provided great service and feel that he added greatly to our experience, and even helped us to avoid many potential problems.
Your money, your call,
Best of luck in your boat search, and enjoy the process,
Tom