Mercury 40HP 2-Stroke Lower Unit Removal

Removing the lower unit from a Mercury outboard has to be done each time you need to make repairs such as replacing a water pump or changing out a prop shaft seal.

Watch the video above and follow the steps below to learn how to remove the lower unit (gearcase) from a Mercury 40HP 2-Stroke outboard.

Tools Needed – Mercury 40HP 2-Stroke Gearcase Removal

  • Ratchet and extensions
  • 13mm, 15mm sockets
  • 16mm wrench
  • 10mm wrench (x2)

NOTE: We removed the lower unit from a Mercury Tracker 40HP 2-stroke motor, but the steps are the same or similar for most small-to-medium sized Mercury outboards.

Mercury Tracker 4-HP 2-stroke gearcase removal

Removing Mercury 40HP 2-Stroke Lower Unit

Step 1. Disconnect the shift shaft by using two 10mm wrenches to loosen and remove the shift shaft coupling nut (located just below the mount halfway down the driveshaft housing).

Mercury Tracker 40 lower unit removal

Step 2. Remove the 13mm trim tab bolt and the trim tab itself.

Step 3. Remove the 15mm lower unit mounting bolt and washer within the trim tab housing.

Mercury 40HP 2-Stroke lower unit removal

Step 4. Remove three of the four 16mm lower unit mounting bolts.

Mercury 40HP Tracker lower unit

Step 5. Support the lower unit so it won’t drop, then remove the last 16mm lower unit mounting bolt.

Step 6. Let the lower unit drop down carefully, away from the outboard and you’re done. 

Mercury 40HP Tracker 2-stroke gearcase removal

NOTE: You may have to rock the lower unit from side to side until it’s free from its mounting dowels.

As noted, the steps for removing the lower unit from a Mercury 40 2-Stroke outboard are the same or similar for most small-to-medium sized Mercury motors. However, if you want to see the gearcase removed on a 4-stroke model, watch the video above to see how to remove the lower unit on a 2003 Mercury Tracker 40HP 4-Stroke engine.

 

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