like rod said, get the motor compression tested. then crawl allover the boat flipping switches, peeking in the bilge, whatever you can think of. check the transom too. some trick you can do by tapping on it with the end of a wood handle or something. not totally sure. beings its only 2400. not sure if having it surveyed is worth it, don't know how much they cost.
need more info, make, year, model engine size, engine hours and so on. personally, i think its only 2400 for a reason, i'd walk away, unless its someone you know who is hooking you up with a really sweet deal.