Mercury’s high-performance 3.0L and 3.2L V6 outboards place heavy demands on the gearcase. Models such as the 250XB, 250XS, 300 Pro Max, 300X, and 300XS run at high RPM with aggressive propeller loads, making the driveshaft seal carrier a critical component.
The new Billet Drivershaft Seal Carrier is a direct replacement for Mercury OEM part numbers 840836, 840836A1, 840836-A1, 840836A2, and 840836-A2, designed to deliver greater service life and reliability in Sport Master and Torque Master lower units.
The carrier is CNC-machined from 6061 billet aluminum, a material known for its excellent strength-to-weight ratio and resistance to fatigue. Precision machining eliminates porosity and dimensional variation common in cast OEM parts, while tight tolerances ensure the driveshaft runs concentrically.
This reduces shaft wobble, minimizes uneven seal loading, and significantly improves sealing performance under high-RPM operation.
To further increase durability in harsh marine environments, the carrier is finished with a blue anodized coating. This anodizing process hardens the surface for superior wear resistance and provides enhanced corrosion protection, particularly valuable in saltwater use where OEM cast parts are prone to pitting. The blue finish also offers clear visual identification of the billet upgrade during service and inspection.
Structurally, the billet design provides greater rigidity than the original Mercury 840836A1 and 840836A2 castings. For high-output models like the 300X and 300XS, this added stiffness prevents micro-movement of the driveshaft, maintaining consistent sealing pressure and protecting the gear oil, bearings, and gears from contamination or premature wear.
Installation is direct, with no modifications required. The billet part dimensions match Mercury carriers 840836, 840836A1, and 840836A2, including their hyphenated catalog variations, ensuring compatibility across 3.0L and 3.2L Sport Master and Torque Master gearcases. This includes the 250XB (3.0L EFI), 250XS (3.0L Optimax), 300 Pro Max (3.0L EFI), 300X (3.2L EFI), and 300XS (3.2L Optimax). It is not used on 2.5L Pro Max outboards or on Sport Jet pump housings.
By combining 6061 billet aluminum construction with a blue anodized finish, the Billet Drivershaft Seal Carrier provides superior strength, corrosion resistance, and long-term stability. For owners of Mercury 3.0L and 3.2L high-performance outboards, it offers a precise, long-term upgrade over factory cast carriers while maintaining full OEM compatibility.
For technical support, contact Mike Hill at +1-714-697-1716 or mike@buckshotracing77.com