What is the flexible raw water pump impeller (impeler / rodete de neopreno), and what happens if a marine engine is started with the seawater intake seacock (válvula de fondo) closed?

1. It is a flexible neoprene rubber rotor that pumps raw seawater; running it dry without water lubrication causes friction heat that destroys the rubber vanes within 30 to 60 seconds, leading to rapid engine overheating
2. It is a brass turbine that automatically opens the seacock when dry
3. It is a plastic filter that converts seawater into diesel fuel
4. It is an electrical alternator component that recharges the starting battery