Have the boat looked at by a mechanic if you can. A compression check should be performed prior to purchase to give you a general idea of how strong the motor is or isn't.
Supercharger should have been rebuilt once already. If owner cannot prove, then you should rebuild just to be safe ($435 if you remove/install yourself and send off for rebuild).
Check drive line for rust and impeller condition. Impeller should be clean and edges smooth.
Check coolant level, oil level, general cleanliness of engine bay and compartments.
Owner should be able to show maintenance history, if not, then be skeptical.
Check to make sure all electronics work (Nav, anchor lights, stereo, digital instrumentation, bilge pump, etc.).
Definitely take it for a sea trial. Make sure boat is close to stated top speed for that model. I would think this boat is capable of 50+.
Remove drain plugs when done. Little to no water should come after your test ride.
