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How to Change the Water Impeller on a 15-HP Boat Motor

    • 1). Remove the bolts that hold the lower part of the unit together with the upper unit. The flat platform between the upper and lower units, directly above the prop is the dividing line. There are two bolts at the front of the unit on the dividing platform, and one on each side toward the front. Above the prop there is a metal plate called a sacrificial anode. It screws in from above the platform. Remove that screw and drop the plate out of its slot. Under the anode there is another screw to remove.

    • 2). Grasp the lower unit securely in both hands. It is heavy. Pull slowly to separate it from the upper unit. If it resists, tap gently with a hammer or rubber mallet. Carefully remove the entire piece that includes long metal shafts that reach up into the upper unit. Do not yank the unit off because there are wires that connect it to the upper unit that will remain connected while you work.

    • 3). Set the lower unit on a clean surface, towel or sheet near the back of the boat so wires remain unstressed. Set the unit on its bottom fin and brace with blocks, bricks, or any stable weight that will hold it upright.

    • 4). Use a socket wrench to remove the nuts on the impeller casing at the base of the metal shaft leading into the lower unit. Place the nuts and washers in a dish to keep them safe and lift the casing up over the top of the shaft. Turn the casing over and pull the impeller out of the center of the casing.

    • 5). Inspect the impeller for damage such as cracks in the rubber, missing blades or burn marks. Replace at any sign of damage, or if unsure of the stability of the impeller.

    • 6). Lift the rubber gasket off the top of the lower unit around the impeller bolt shafts and the shaft. Pick up the metal/aluminum gasket directly below it and then remove another rubber gasket. Replace the first gasket, replace the metal gasket, and place the final gasket on top of the lower unit, around the shaft and over the bolt shafts.

    • 7). Grease the impeller around the blades. Place over the shaft and slide to the base of the lower unit. Lightly grease the inside of the casing and slide it over the shaft and down over the impeller.

    • 8). Replace all nuts and washers. Tighten with a crescent wrench and firm with a socket wrench.

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