The Buckshot Racing #77 1.75 Right-Hand (RH) Gear Set Kits are engineered to replace Mercury OEM Part Number 859321T04. Designed for Mercury Racing 3.0L Sportmaster Gearcases and Torquemaster Lower Units, this gear set delivers durability, smoother power transfer, and consistent high-speed performance under the most demanding conditions.
 
Whether you’re pushing the limits or fine-tuning for recreational performance, our gear set kits offers proven reliability and precision engineering that elevates your boating experience.
 
Key Features and Specifications
SpecificationDetailsGear Ratio1.75:1CompatibilityMercury Racing 3.0L Sportmaster Gearcases & Torquemaster Lower UnitsReplacement for OEM Part859321T04RotationRight-Hand (RH)MaterialHeat-treated, high-strength steelPrecision ManufacturingAerospace-grade CNC machiningSurface FinishMicro-polished for reduced frictionDurabilityEngineered for high torque and RPM 
Optimized 1.75:1 Gear RatioThe 1.75:1 ratio strikes the perfect balance between top-end speed and acceleration, making it ideal for high-performance Mercury Racing 3.0L Sportmaster gearcases and Torquemaster lower units. This gear set enhances thrust efficiency, ensuring maximum power delivery for high-speed runs and tight control.
 
Built for Durability and High-Torque ConditionsMade from heat-treated, high-strength steel, the Buckshot Racing #77 gear set withstands extreme torque and RPM conditions common in performance boating and offshore racing. Our precision manufacturing process ensures tight tolerances for enhanced durability and a perfect fit.
 
Reduced Friction and Heat Build-UpThe gears feature a micro-polished surface finish to minimize friction and reduce heat generation. This translates into longer gear life, smoother operation, and reliable performance during extended high-speed use.
 
Direct Replacement for Mercury OEM Part 859321T04This kit is a direct-fit replacement for Mercury OEM 859321T04, ensuring seamless integration with your 3.0L Sportmaster or Torquemaster gearcase. No modifications are required, making installation straightforward and hassle-free.
 
Proven High-Performance EngineeringRigorous real-world and simulated testing ensures the Buckshot Racing #77 gear set delivers consistent performance under race-level stress. It provides tighter, more reliable power transfer, critical for maintaining control at high speeds or during aggressive maneuvers.
 
Applications
The 1.75 RH Gear Set Kit is ideal for:
High-Performance Boating: Rebuild your Mercury Racing 3.0L gearcases. Designed to handle high-torque, high-RPM environments with precision.
Recreational Performance Boating: Improve acceleration and top-end performance with unmatched reliability.
 
Installation and Fitment
 
The Buckshot Racing #77 1.75 RH Gear Set Kit is a direct replacement for Mercury OEM Part 859321T04. It is fully compatible with:
 
Mercury Racing 3.0L and 3.2L Sportmaster Gearcases
Mercury 3.0 Liter Torquemaster Lower Units
 
Professional installation is recommended to ensure proper fitment and alignment for optimal performance.
 
The Buckshot Racing #77 1.75 Right-Hand Gear Set Kit is engineered to meet the demands of high-performance boating, providing exceptional durability, precision, and efficiency.
 
Replacing your  Mercury OEM Part 859321T04, this gear solution for Mercury Racing 3.0 Liter and 3.2 Liter XS Sportmaster gearcases and Torquemaster lower units will get you running strong on the water again.
Please note prop shaft seals for the large 1.25" shafts are not included in this kit. 
 
Contact Mike Hill with any questions at +1-714-697-1716 or mike@buckshotracing77.com