How to Change a Prop Outboard

When you want to change a prop on an outboard, you are actually tackling two tasks -- removing a prop, or propeller, and replacing a propeller. When you replace the propeller, it may be the same propeller you took off the propeller shaft, or it may be an entirely new propeller. Either way, the propeller is not always the only thing on the propeller shaft. There may be spacers or washers, including a special washer called the thrust washer. The thrust washer transfers the power from the propeller shaft to the propeller.

Things You'll Need

  • Wire snips
  • Wood, 2-by-4-by-36 inches
  • Needle-nose pliers
  • Propeller wrench
  • White marine grease
  • Marine cotter pin
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Instructions

  1. Propeller Removal

    • 1

      Disconnect the battery (see instructions in "Warnings"). Inspect the center of the propeller hub, looking for a cotter pin that runs through the propeller shaft, and the castellated nut on the end of the propeller shaft. Cut the bent ends of the cotter pin off with a pair of wire snips. Grab the loop at the end of the cotter pin with the needle-nose pliers and pull the cotter pin from the castellated nut.

    • 2

      Slip a piece of wood, 2-by-4 inches, 36 inches long, between one of the propeller blades and the right side of the horizontal anti-ventilation plate above the propeller.

    • 3

      Fit the propeller wrench onto the castellated nut and brace your right foot against the bottom of the piece of wood that you placed between the propeller blade and the outboard's anti-cavitation plate. This prevents the propeller from moving as you turn the propeller wrench counterclockwise to remove the propeller nut from the propeller shaft.

    • 4

      Inspect the spacer that you expose by removing the propeller nut -- its outer face is different than its inner face. Slide the spacer from the shaft.

    • 5

      Slide the prop off the propeller shaft. Note whether or not the thrust washer stays inside the propeller -- in some models, it will. In others, it will remain on the propeller shaft. Pull the thrust washer from the propeller if it comes off with the propeller.

    • 6

      Turn the propeller shaft in your fingers, looking for twisted splines or signs of uneven wear. Remove any fishing line that's wrapped around the shaft. The monofilament normally used in fishing can cut deep grooves in the shaft and destroy the propeller shaft seal, leading to gear-case damage.

    • 7

      Turn the thrust hub around in your hands, looking for bits of black rubber. Inspect the grease on the splined propeller shaft as well. These bits of rubber indicate that the propeller has slipped on the shaft and requires professional repair before reinstallation.

    Propeller Installation

    • 8

      Spread a generous helping of white marine grease over the propeller shaft's splines. Slide the thrust hub over the splines so that it fits onto the shaft facing the same direction it faced when you removed it.

    • 9

      Fit the propeller onto the propeller shaft and turn it, so that the hub's internal splines align with the splines on the shaft. Push the propeller forward until it seats on or against the thrust washer.

    • 10

      Fit the spacer -- the one with one side different from the other -- back onto the face of the propeller hub. Be certain you put it back on facing the way you removed it. Thread the propeller nut back onto the shaft.

    • 11

      Insert the 2-by-4 between one blade of the propeller and the motor's anti-ventilation plate. Move your left foot forward, to hold the bottom of the 2-by-4 so the propeller blade can't turn clockwise. Tighten the propeller nut to 55 foot-pounds with a torque wrench.

    • 12

      Pick up a new cotter pin with needle-nose pliers. Push the cotter pin through the hole in the propeller nut and through the propeller shaft. Move the propeller nut a bit tighter if you need to, to get the pin to go through the shaft. Bend the ends of the cotter pin in opposite directions.