Mercury Tracker 25 Gearcase Oil Change

When was the last time you changed your outboard’s gearcase lube? Manufacturers recommend the lower unit oil of an outboard be changed after every 100 hours of use or once a year. 

Watch the video above or follow the steps below to change the gearcase oil in a Mercury Tracker 25 outboard.

NOTE: The steps to change the lower unit oil on a Mercury Tracker 25 are the same or similar for almost all outboard makes and models. 

Tools and Parts – Mercury Tracker 25 Gearcase Oil Change

Buy Mercury lower unit oil

Buy Mercury gear lube pump

PRO TIP: The OEM Mercury brand gear lube pump comes with the correct attachment for Mercury outboards, so you won’t have to buy an additional adapter.

2001 Mercury Tracker 25 outboard engine lower unit oil change

How to Change Mercury Tracker 25 Gearcase Oil

Step 1. Remove the vent screw and washer from the top right side of the lower unit.

2001 Mercury Tracker 25 outboard motor lower unit oil change

Step 2. Position a drain pan under the lower unit, and remove the drain/fill screw and washer from the bottom right side of the lower unit. Let the gearcase oil drain out.

2001 Mercury Tracker 25 outboard lower unit oil change

NOTE: You should inspect the vent screw washer and the drain/fill screw washer for wear, and replace them if necessary. To ensure there are no oil leaks, the washers should be replaced every couple of lower unit oil changes, regardless of their condition. 

Step 3. Attach a Mercury gear lube pump to a quart bottle of Mercury SAE90 gear lube, then attach the other end of the pump to the drain/fill hole in the lower unit.

2001 Mercury Tracker 25 outboard motor gearcase lube change

Step 4. Slowly pump the new gear lube into the lower unit until it starts to flow out from the vent hole.

2001 Mercury Tracker 25 outboard gearcase lube change

Step 5. Reinstall the vent screw and washer into the lower unit.

Mercury Tracker 25 outboard gearcase lube change

Step 6. Remove the gear lube pump, and quickly reinstall the drain/fill screw and washer into the lower unit.

Mercury Tracker 25 outboard lower unit oil change

Step 7. Clean off any spilled oil from the lower unit using contact/brake cleaner and you’re done. 

Mercury 25HP outboard lower unit oil change

Watch the video below to learn how to do a gearcase pressure test on a Mercury Tracker 25 outboard.