Mercury Tracker 25 Lower Unit Installation

After servicing your Mercury outboard’s lower unit, you’ll obviously need to reinstall it back onto the outboard itself. 

Watch the video above and follow the step-by-step walkthrough below to reinstall a Mercury Tracker 25 lower unit. Use our Mercury Tracker driveshaft parts diagram below for additional reference.

Mercury Tracker 25 lower unit exploded parts

Tools and Supplies Needed – Mercury Tracker 25 Reinstall Lower Unit


  • Ratchet
  • 10mm, 16mm sockets
  • Torque wrench


NOTE: We worked with a 2001 Mercury Tracker 25 EL engine, but the steps are the same or similar for most outboard motor makes and models. 

Mercury Tracker 25 lower unit installation

Remounting the Lower Unit to the Mercury Tracker 25EL

Step 1. Lube the driveshaft/input shaft and the water tube sleeve on top of the water pump housing with PTFE marine grease.

Mercury Quicksilver PTFE grease

Step 2. Make sure the shift shaft and the gear shift mechanism on the outboard are in neutral.

Step 3. Apply blue threadlocker to the four 16mm lower unit mounting bolts.

Mercury Tracker 25 gearcase remount

Step 4. Slide the drive shaft and shift shaft up into the driveshaft housing.

Step 5. Reinstall the four 16mm lower unit mounting bolts, and torque them to 40 foot-pounds.

Mercury 25 lower unit installation

Step 6. Reinstall the shift shaft retaining pin, and push the retaining clip back over the retaining pin.

Mercury 25 gearcase installation

Step 7. Reinstall the starter and its two 10mm mounting bolts, and reconnect the wire leading to the starter solenoid.

Mercury outboard lower unit installation

Step 8. Reinstall the air intake cover and you’re done.

Mercury Tracker 25 gearcase reinstall

As previously mentioned, the steps to reinstall the gearcase onto a Mercury 25 are the same or similar for all outboard models. However, if you want to see this same job done on a higher horsepower engine, watch the video below to see how to remount the lower unit on a Mercury 200 outboard




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