Mercury & Mariner 1988-2006 L4 2-Stroke 100-125 HP Gearcase Parts Diagrams

Welcome to the OBParts parts diagram and replacement parts hub for Mercury & Mariner L4 100-125 HP outboard engines, covering models built between 1988 and 2006. Browse comprehensive parts diagrams for the four-cylinder lower unit and explore a full range of replacement components, including gearcases, water pump kits, impellers, bearings, seal kits, propshafts, shift shafts, clutch dogs, and more. Whether you're rebuilding or repairing, we offer OEM-equivalent quality at competitive prices, with trusted brands like Red Rhino, EMP, Sierra, and more. You can easily find the components you need by navigating through clear categories and diagrams.

We offer a complete rebuild kit for this gearcase as well as individual aftermarket parts. Please select from the following list or from the photos below:

Complete Rebuild Kit

The following parts correspond to the numbers on the diagram to the right:

1. Inner Forward Gear Bearing
2. Outer Forward Gear Bearing
3. Top Drive Shaft Bearing
4. Bottom Drive Shaft Bearing
5. Reverse Gear Thrust Bearing
6. Forward Carrier Gear Bearing
7. Aft Carrier Bearing
8. Cam Follower Kit
9. Gear Set
• 3 Jaw
• 6 Jaw
10. Reverse Clutch Dog
• 3 Dog
• 6 Dog
11. Clutch Dog Pin
12. Clutch Dog Spring
13. Reverse Prop Shaft
• 3 Jaw
• 6 Jaw
14. Bearing Carrier
15. Drive Shaft
16. Pinion Nut
17. Shim Kit

 We also offer the following items:

• Shift Cam
• 3 Jaw
• 6 Jaw
• Water Pump Kit
• Lower Seal Kit
• Bearing Kit