If your just looking, general condition and maintenance records. Corrosion on engine parts and jet pump. If it looks good it probably is. If your test driving. Hard start issues, hopefully with a cold engine. Vibration issues. Oil leaks, bilge should be pretty. Oil quantity on dipstick and color of oil. Carbon seal dust and dry bilge. General smooth acceleration, make sure the VTS and IBR work without codes. WOT rpm and top speed. Look up values on internet for the ski. Within a couple hundred RPMS and 5 mph. Scroll thru active code list on MFD display. Should be no active codes.