Assuming everything is in good condition, how do I determine if the price someone is asking for a boat is a good deal or if it's too high? I've heard of nadaguides.com, but I've punched in information about boats before and it always seems like a very low estimate. Boats last a lot longer, so it doesn't seem to be as easy as pricing out a car. I'd like to use more than a gut feeling to make a decision. Any thoughts?

Boat Trader Online. http://www.boattraderonline.com/newadsearch.html

Scroll down the menu on the left side and click on 'Price Checker'. Type in the year, make and model of the boat you're looking at and it will bring up all current ads in the country matching your criteria. That way you can compare against what others are currently asking for the same boat.

Boats dont last THAT long. A boat will a while, but things always continually break or just need replacement. Boats have very LOW resale values. But also it depends on whos buying it and what part of the country your in. Up in WA, a boat for 8,000 up here migh only be 4,500 in Alabama.

Skwerl, that idea works pretty well. Thanks for your help.

Does anyone know if there is a "blue book" for boats?

For loan value(s) banks will use NADA guide exclusively....

You need to start researching.  There are several places on the net that used boats are sold at. Check you local papers.  You should start getting an idea how much to expect a boat of this particular model, year, size and horsepower should cost you.  Check with NADA.  Yes, it's kicks out low numbers but as stated that's what the bank will go by for loan amounts, not necessarily what the boat is really worth. Lots of things come into play on what a boats worth.  

Cart7 is right. Use all the media resources you can to see what people are asking for particular boats. This will give you a good idea as to what a certain boat w/ a certain moter in a certain condition is going for. After some research when one comes along that tickles your fancy you will have a pretty good idea if it is a deal or something to pass on.