Water leaks, how easy does it shift in and out of fwd/reverse, low voltage alarm/check engine light/siren, condition of the steering cable, i.e. how easy is it to turn, ballast pumps-make sure they work in both directions fill/empty, check oil and tranny fluid, when was the impeller last changed, take it up to WOT for at least 1 minute. That's about all I can think of off of the top of my head. Lastly,
CHECK TO MAKE SURE ALL BOARD RACKS WORK. 2003 racks are worth more than gold. They were only made for one year and they break. I have fixed a couple if they aren't too bad. Shoot me a PM if you need a lesson. If you get this boat you will want to eventually upgrade to the 2004 Clamping racks, but this requires drilling new holes in the tower.