The Bearing Carrier Retainer Nut Tool from Buckshot Racing #77 is a precision-engineered service tool designed specifically for Mercury Racing outboards equipped with the larger 1.25-inch "fat shaft" propeller shafts.
This tool is a direct replacement for Mercury OEM part number 91-840393 and offers marine technicians and high-performance boaters a durable, high-strength solution for maintaining Mercury Racing 2.5-liter and 3.0-liter SportMaster and TorqueMaster lower units.
Compatible with Mercury Racing 2.5L engines such as the 2.5 EFI Offshore, 260 HP, and 280 ROS HP, 300 Drag models, as well as 3.0L outboards like the 300X and 300XS, this specialized wrench is critical for servicing high-performance gearcases.
These V6 two-stroke and OptiMax motors, producing between 200 and 300 horsepower, feature heavy-duty gearcases that require a properly sized carrier nut tool for safe and effective maintenance.
Built from premium materials, the retainer nut wrench is engineered to handle the extreme torque needed to remove and install the 4-3/8 inch diameter bearing carrier retainer nuts used with Mercury’s high-output gearcases.
This tool securely engages the slots of the retainer nut, minimizing the risk of slippage, tool damage, or gearcase thread damage during service procedures. Its precision fit and strength help maintain critical tolerances required for Mercury Racing SportMaster and TorqueMaster gearcase reliability.
To service the bearing carrier retainer nut, first remove the propeller and hardware from the 1.25-inch diameter prop shaft. After cleaning the work area, inspect the locking tab washer and bend the tabs away from the nut.
Then fit the bearing carrier tool securely over the retainer nut, ensuring full engagement with the notches. Attach a breaker bar or torque wrench and apply a controlled force and possibly heat to loosen any built-up corrosion in the threads and remove the nut.
During reassembly, the nut should be torqued to Mercury's specified value, and the locking tab washer must be repositioned and bent back into the nut’s slots to ensure secure retention.
Using the Bearing Carrier Retainer Nut Tool allows marine technicians and serious performance enthusiasts to service Mercury Racing lower units properly, preserving bearing preload, shaft alignment, and water seal integrity.
High-horsepower engines such as the Mercury Racing 2.5L 280 HP and the Mercury Racing 3.0L 300XS rely on precise gearcase assembly to maintain performance and reliability, making the use of an accurate, purpose-built tool critical.
The Wrench is specifically designed to match the service needs of SportMaster and TorqueMaster gearcases installed on 2.5-liter and 3.0-liter Mercury Racing outboards. It delivers the strength, precision, and OEM-level compatibility required for professional maintenance on high-performance V6 engines equipped with the larger 1.25-inch "fat shaft" propellers.
Whether rebuilding a Mercury 2.5L EFI race engine or servicing a 3.0L offshore fishing motor, the carrier retainer wrench from Buckshot Racing #77 provides a reliable and durable tool solution for critical lower unit maintenance.
Contact Mike Hill at +1-714-697-1716 or email mike@buckshotracing77.com for technical support.