MerCruiser Sterndrive Lower Unit Removal & Disassembly

Knowing how remove the lower unit on a sterndrive is essential for regular service and repairs.

Watch the video above and follow the steps below to remove the lower unit from a MerCruiser Bravo 2 diesel sterndrive. This walkthrough also covers how to disassemble the lower unit to replace leaking oil seals or worn bearings. 

Tools Needed - Mercruiser Bravo 2 Sterndrive Breakdown

• Ratchet
• 14mm, 16mm, 32mm, 36mm sockets
• Slide hammer/puller
• Mercury driveshaft adapter
• Mercury retainer ring tool

Step 1. Place a drain pan under the lower unit. Next, remove the oil drain/fill plug from the bottom of the lower unit and the vent plug from the upper right-side of the driveshaft housing, and let the gearcase lube drain out. 

Step 2. Bend back the tabs on the tab washer to release the prop nut, then remove the 36mm prop nut and the tab washer, the propeller and the thrust hub behind it.

Step 3. Remove the trim tab anode.

Step 4. Support the lower unit to prevent it from falling, then remove the 16mm lower unit mounting bolts. There are three bolts on either side of the lower unit and one bolt within the trim tab anode housing.

Step 5. Remove the lower unit from the driveshaft housing.

Watch the clip below to see the lower unit removal segment of our MerCruiser Bravo 2 lower unit video.

MerCruiser Bravo 2 Sterndrive Lower Unit Disassembly

Step 6. Bend back the tabs on the tab washer to release the bearing carrier assembly’s retainer ring. Use a Mercury retainer ring tool to remove the retainer ring and tab washer.

Step 7. Remove the bearing carrier assembly with a puller tool or slide hammer.

Step 8. Pull the prop shaft out from the gearcase.

Step 9. Hold the drive shaft with a Mercury driveshaft adapter tool connected to a 32mm socket and remove the 14mm pinion gear nut from within the gearcase.

Step 10. Remove the clamp plate from the top of the lower unit.

Step 11. Remove the O-ring, spacer, shims and tab washer from the lower unit, then lift the driveshaft out from the lower unit.

Step 12. Remove the O-ring, thrust ring and load ring from the gearcase. 

NOTE: You may have to use a slide hammer to remove the thrust and load rings.

Step 13. Remove the pinion gear from the gearcase.

Step 14. Using a slide hammer/puller, remove the driveshaft bearing race from the top of the lower unit and the prop shaft bearing race from within the gearcase.

Step 15. Remove the shims beneath the driveshaft bearing race and the prop shaft bearing race and you’re done.

Watch the clip below to see the lower unit disassembly segment of our MerCruiser Bravo 2 lower unit video.