It all comes down to dollars above what you could do otherwise.
The broker does a lot of administrivia you could do yourself or hire someone else to do.
They best be selling your boat at a higher amount than what you think is a reasonable hourly rate for that administrivia.
That's one way of looking at it. But only if you include some of the following under that 'administrivia'. Like that term, by the way.
- responding to all inquiries
- scheduling showings
- dealing with deadbeats, dreamers and jerks
- negotiations on price and all terms of sale
If you need to hire someone for that, you're pretty much forced into the arms of the broker, and if you are then you're on their turf in terms of the pricing model.
I kind of think it's much the same on the buying side these days. Some buyers expect to have a hopefully trusted intermediary at their side through the process, and they are likely to buy a brokered boat. For others, as documented here, brokers are just in the way.
So really there are two questions a seller should ask, and they're both important.
1) am I comfortable with the administrivia and do I like selling stuff?
2) who is my likely buyer? How much value add will the broker represent for them?
Seems to me that a boat like yours is going to have specialized appeal. Most buyers will have guided themselves to that boat IMO. Most of them are not going to need a lot of hand-holding.
So it's hard to make a case for a broker if you've answered Yes to #1.
I wouldn't discount the value of this type of forum. You may get an email out of the blue from a genuine buyer.