How many of you go by the book N.A.D.A. for boat values when purchasing a boat? Would you pay over book? Why and why not?

Do the research yourself based on what other similar boats are listed and "SELLING" for.
A boat or anything else for that matter is only worth what someone is willing to pay for it.
The problem with NADA is that accessories/rigging/motors are hard to put a price on and they vary greatly in price. Good luck with your search.

Bought 8 boats in 11 years. Never paid NADA retail, some of them were below NADA wholesale. Depends on what it's worth to YOU.