When the boat is out of the water, close the seacock, remove the sea strainer lid, and put a hose in the strainer bowl. Use a bungee to hold it in place. Turn the water on and let it run to overfilling and check that the bilge pump comes on (just an added item covered). Start the boat and check for water out the exhaust. Reverse the process when complete but keep the seacock closed to keep the pump primed for next startup. It’s also a good idea to wash down the whole engine room (especially around the transmission and engine mounts) with fresh water to wash off any salt spray/mist from the shaft.
Curt