Your Yamaha 15 horsepower outboard motor is used for smaller watercraft. It is still a durable motor that does not require much in terms of maintenance. However, from time to time you may have to change the water pump. The water pump on your Yamaha outboard, not unlike the coolant system on a car, is responsible for circulating water through the motor to keep it cool. It takes approximately one hour to change the fuel pump on your Yamaha outboard.
Use your socket set to remove the retaining bolts that hold your Yamaha outboard's lower unit in place. Remove the lower unit and set it on flat surface.
Remove the bolts holding Yamaha's water pump cover in place and then slide the cover off.
Use your socket set to then remove the water pump's retaining bolts. Once you take these off, slide the old water pump and the impeller off your Yamaha's driveshaft.
Slide the new impeller and the new water pump onto the driveshaft.
Insert the water pump's retaining bolts and then tighten them with your socket set. Replace your Yamaha's water pump cover and replace its retaining bolts too.
Reattach the lower unit of your Yamaha and replace the bolts that fasten the lower unit to the top section of your outboard motor.