How to Install a Lower Unit Shift Rod on a 40 HP Mercury

A bent shift rod in a 40-horsepower Mercury outboard's lower unit usually happens over time, with use. It will -- eventually -- prevent you from changing gears. While it isn't a normal occurrence, it happens often enough that a shift rod replacement kit is available. The kit come with all the parts necessary to install a new shift rod, except the shift rod. With the kit and the tools you should have on hand to keep your Mercury running, install the shift rod yourself.

Things You'll Need

  • 7 mm socket
  • Shift rod replacement kit
  • White marine grease
  • Shift rod
  • Hammer
  • Thread locking compound
  • Torque driver
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Instructions

    • 1

      Remove the two shift rod retainer securing bolts using a 7 mm socket. Pull the old shift rod from the shift rod cavity. Realign the hole in the shift cam with the gear case shift rod bore.

    • 2

      Install a new O-ring from the shift rod replacement kit onto the shift rod seal housing. Apply white marine grease to the shift rod seal and set onto the shift rod seal retainer. Push the seal retainer downward, moving it into place on the shift rod.

    • 3

      Push the short-spline end of the lower shift rod into the shift rod cavity. Turn the rod so its splines index with the splines on the shift cam splines. Tap the seal retainer into the shift rod cavity, using light taps from a hammer.

    • 4

      Apply thread locking compound to the threads of the two 7 mm rod retainer securing bolts. Thread the bolts into place and tighten to 60 inch-pounds with a torque driver. Install the E-clip from the replacement kit around the top of the shift shaft. Set the coupler and nylon spacer on top of the shaft.