A summary of important considerations from Judge
Brittleness – if any of the plastic feels brittle (from being in the sun or just plain old) do not buy – and maybe don’t even take as
a gift – it’s up to you on that one. You need to know what a new kayak feels like before you start checking old ones.
Structure – look for modifications, holes and visibly deep scrapes in the hull. If you are concerned – ask the seller if you can fill it up with water. By doing this on dry sidewalk, you should be able to tell if it leaks (and there will probably be a lot more pressure on the hull when it’s full of water than it will be when you are on it in the water). Modifications – any holes put into the hull are a possible source of leaks. Check them out. Real small holes (like for pop rivets) can be filled with plastic and a heat gun (from Home depot), hot glue or even some shoe goo. Look it over top and bottom -particularly to see how the wear is around the supper holes on the bottom – a place of particular wear as you land on the beach.
Form – The plastic boat can be misshapen as a result of being tied to a car or truck in hot weather. They say in the OK book, that they will regain their old shape if allowed to heat and cool on a level surface with no tie downs. If you find a boat that seems to have cooled to the wrong shape, you may or may not be able to get it right again. Also, the booklet says that hanging them by their handles can make them warp. Again, I don’t know if they will “right” themselves if allowed to heat and cool on a flat surface – Maybe this is a question for a dealer or manufacturer.