How to Change an Overheated Impeller Sending Unit on a 1998 Force 120

The 1998 Force 120 is an outboard boat motor that uses an impeller sending unit to signal when the boat's water pump is not functioning properly and when the motor begins to overheat. The water pump, where the impeller is housed, circulates water through the engine to keep it cool, much like radiator and water pump system in a car. If the water pump does overheat, however, it is possible that you will have to change the impeller sending unit when you replace the impeller.

Things You'll Need

  • Screwdriver
  • Pliers
  • Marine grease
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Instructions

    • 1

      Pull the heat tube sensor unit through the rubber grommet mounted on the side of the water pump housing.

    • 2

      Remove the other end of the heat tube from the water pressure gauge. Loosen the clamp that holds the tubing to the port on the gauge with a screwdriver.

    • 3

      Slide the clamp over the rubber end of the impeller sending unit heat tube. Slide the tube onto the gauge port with a pair of pliers. Tighten the clamp with the screwdriver.

    • 4

      Apply a small amount of marine grease on the sensor end of the heat tube and then use pliers to pry it back through the grommet on the impeller pump housing.