This bearing for Mercury Big Prop Shaft Carriers is a precision-engineered component that plays a critical role in maintaining the performance and reliability of Mercury high-output outboards, particularly in racing and competitive fishing applications.
 
Specifically designed for use in Mercury 2.4 Liter CLE (Crescent Leading Edge) gearcases, as well as the 2.5, 3.0, and 3.2 Liter Sportmaster and Torqmaster gearcases, it supports the high-performance needs of Mercury Racing and Pro XS engines used in tournament bass boats, offshore race boats, and high-speed recreational craft.
 
Identified by OEM Mercury part number 817072, this bearing is manufactured by Koyo JTEKT—a global leader in the design and production of high-quality bearings and precision automotive components. Koyo JTEKT USA operates advanced manufacturing facilities in the United States, known for their rigorous quality control, precision engineering, and commitment to ISO 9001 and TS16949 quality standards.
 
Koyo bearings have a longstanding reputation for durability, reliability, and performance under extreme operating conditions, including high-speed racing, heavy industrial use, and demanding marine environments. Their bearings are trusted by top-tier manufacturers across industries for applications requiring exceptional load capacity, thermal stability, and corrosion resistance.
 
Crafted from high-strength alloy steel, this bearing incorporates hardened and precision-ground raceways designed to handle extreme axial and radial loads while resisting wear and corrosion from saltwater exposure and high-speed operation. The advanced surface finish reduces friction and minimizes heat generation, essential for maintaining hydrodynamic efficiency in high-RPM conditions. Koyo’s precision manufacturing processes ensure micron-level tolerances that maintain precise prop shaft alignment, minimizing vibration, power loss, and gear wear in Mercury gearcases.
 
During installation, the carrier housing must be cleaned thoroughly, and a thin layer of marine-grade anti-seize lubricant applied to prevent galling and ease installation. The bearing should be pressed into place using a hydraulic press or precision bearing driver tool, ensuring even pressure and square seating.
 
Torque specifications for the carrier retaining nut (or spanner nut) are critical and should be set to 90–110 ft-lbs (122–149 Nm) using a calibrated torque wrench and appropriate spanner socket. After assembly, it is essential to confirm the carrier pre-load and shaft end play using a dial indicator, with end play typically between 0.002–0.004 inches (0.05–0.10 mm) to maintain Mercury’s performance and durability standards.
 
As an OEM-approved component made by Koyo JTEKT USA, this bearing reflects the high standards of both Mercury Marine and Koyo for precision, durability, and performance. Koyo bearings are renowned for their use in Formula 1, NASCAR, and other high-stakes motorsports where bearing failure is not an option. Their engineering expertise translates seamlessly into marine applications, where high-speed, high-load, and corrosive environments demand components of uncompromising quality. The bearing’s corrosion-resistant coating, precision-ground elements, and exceptional load ratings ensure long-term durability and performance even under extreme marine conditions.
 
This bearing also corresponds to several other Mercury part numbers, including Mercury 15265A1, 15265A2, and 23-883478, covering various CLE, Sportmaster, and Torqmaster assemblies. Always consult Mercury Marine service manuals and rigging guides to confirm exact compatibility with specific outboard models and serial numbers.
 
When installed properly, this bearing maintains precise prop shaft alignment, supports smooth and efficient rotation, and delivers the reliability needed for high-performance marine environments. Whether used in competitive offshore racing, tournament bass fishing, or performance recreational boating, it provides the durability, precision, and efficiency demanded by Mercury Racing professionals and marine enthusiasts alike.
 
Contact mike@buckshotracing77.com or +1-714-697-1716 with any questions.