I have owned a 1989 Rangerboat with the original Johnson 150 motor since 1999. The boat was purchased from a friend who took excellent care keeping it waxed and serviced like a pro. Even so, it has had, the motor rebuilt, the flooring and carpet replaced, misc. electrical upgrades and basic maintenance. With that said spring is not the correct time to buy a boat. I would spend the money to have the boat checked over professionally there is nothing worse than finding out the motor is at the end of it's life on an old boat and needs a $12,000.00 motor. Same with any of the other major areas for rot and electrical issues. While you may have to survey 2 or 3 boats it will be the best money you can spend. Go slow and remember the fall is the best time to buy a boat it will be cheaper and you will have all winter to putter and fix it just the way you want.
Happy hunting
Art