Good advice all.
I would add;Get a pro to inspect the boat (surveyor) as one of your terms;
Tell your boat broker
(if you have one) exactly what you wish to do, and let him communicate with the seller or if no *broker,
It works the same Buyer dealing with Seller.
Simply decide in advance, what your limits are, stick to them and don't be swayed by the sales talk.
For me, I usually have 3 prices (including set of terms) in mind and hold them close to my vest (like poker).
1st offer/price/terms the seller would be near crazy to accept. (and I would probably buy it, even if I didn't need it)
2nd offer/price/terms is what I am ok to pay, and would feel certainly meets my requirements.
3rd offer/price/terms is the most I will pay regardless how much I love it, and it would only be after much research
to ensure I have explored the first two offer/price/terms were not acceptable to the seller.
Then walk away and forget it, there will be other boats. After all, you have from now to spring to find another one. The seller only has one boat to sell. As buyer, you have all the strength really, without a buyer, there is no seller, only a wanna be seller.
*Boat brokers don't shoot me!!