I've just negotiated the purchase of my second boat. The sellers asking price was very reasonable, and had already been discounted for some needed repairs, so he wasn't willing to accept a lower offer. However, I was able to negotiate some other benefits.
Since I'm buying in the fall, I wanted the boat to remain on his property for the winter. The seller also agreed to shrink-wrap the boat. On top of this, the seller has allowed me use of his mooring for the next season. All of this has added up to several thousand dollar worth of saved storage, maintenance, and mooring fees.
If the asking price is firm, look for other concessions.