Re: NADA used boat prices
As Bubba said, look for the notes under each manufacturer and model. That will tell you if the trailer is included and even if an outboard motor is included in the price given. You typically find this sort of 'package' pricing with boats that are sold as such.
If there are not notes mentioning the trailer, etc. then you can add it in. FWIW - trailers sell better by themselves, and don't add a whole bunch to the value when a boat is sold with a trailer. Sooo, I would not add the full value of a trailer to come up with a fair market price for a used boat.
As far as the usefulness of NADA . . . I have found that it is more of a depreciation schedule than a market guide. Being such, it tends to overstate the fair market value of newer boats and understates the fair market value of older boats. With boats in the 12 year old range, NADA can be pretty good. I have seen wierd deviations to that general rule, though. So, you always want to use other information to assess fair market value.
BUCvalue is another price guide and tends to be more accurate to the market. There is also a matter of looking at the range of asking prices for same/similar boats. Similar/same boats tend to sell from the bottom of the range of asking prices. The folks in the higher range are just behind in their mortgage, or have other needs for large amounts of money.
Can you tell us a bit more about the type of boats that you are looking at?