Common Sense
You will definately need a survey, however, use common sense when looking the boat over. Is it a fixer upper or does it look like it's been well kept and cared for? Don't let your want get in the way of good sense. If the boat is a mess, take a real close look at it. If the seller did not take care of the routine maintenance stuff, cleanliness and small repairs, etc., he probably didn't care of the serious matters. Bottom line, is that if you are serious about buying, make your offer for the final sale contingent on the survey, and get something in writing by the seller about what repairs if any he will be responsible for just in case the survey goes South. Lots of sellers get bugeyed when you start talking about repair responsibility. The reaction that you get may give you some insight about unseen needed repairs.