Make sure all switches, electrical, electronics, bilge pumps, lighting, gauges, etc. work correctly. Check fuse panes breakers for corrosion loose connections. Check for cracks or very deep gouges in hull. Look for hull deformaties. Open bilge access hatch and smell the bilge for any fuel leaks. Check fuel lines and fuel sender for leaks. Check hydraulic steering for leaks and smooth operation. Check motor trim and tilt, prop for dings or bent blades. cracks or leaks in lower unit. You get the idea.
Now for the most important,,,,,,sea trial. If you sure you want it require a sea trial. Check profile static in the water. Operate trim underway. check all thru hulls and bilges while static and underway. Make sure motor reaches max RPM (typically 5000-5500rpm). Shift forward and reverse several times.....should be smooth and not jam or grind. Check acceration without hesitations or stumbles.
I'm sure others here will add more. Good luck, hope it goes well.
Capt. Bill A.
Vessel: Recycled Plastic