How do you change water pump impeller in 2001 mercury 115 hp outboard?

To change the water pump impeller on a 2001 Mercury 115 HP outboard, first, remove the lower unit by disconnecting the shift linkage and unbolting the lower unit from the powerhead. Once the lower unit is removed, take off the water pump cover by unscrewing the screws and carefully lift the old impeller out. Install the new impeller, ensuring it is oriented correctly, and reassemble the water pump cover and lower unit. Finally, reconnect the shift linkage and secure the lower unit back to the powerhead.