Make sure the battery has a good charge
Clean the terminals and reconnect them to the battery
Check engine oil level
Check trans fluid level
Check v drive oil level (if applicable)
Make sure all plugs are in and snug
Check all hoses and make sure they are connected and tight
Make sure the water strainer bowl is tight and has an o-ring in there (if applicable)
Check the prop and prop nut to make sure they are tight and in good shape. Make sure you have a STAINLESS STEEL cotter pin on there
Reinstall drain plug(s)
Make sure the blower, horn, bilge, etc work
Water test the boat looking for the following:
All guages function properly
The impeller is drawing water to cool the engine
No leaks from hoses or plugs on engine
Check for vibrations
Check condition of steering (is it getting stiff?)
Check the movement of the shift cable (is it getting stiff?)
Check the shaft packing to make sure it doesn't leak too bad (a little drip is fine)
Check rudder packing to make sure it isn't leaking
Fill and empty ballast tanks (if applicable) to make sure they are working properly
Enjoy Summer!!