The integrity of the gearcase threads in Yamaha four-stroke outboard lower units is critical to long-term reliability and safe operation. Corrosion, galling, or cross-threading of the carrier ring nut threads can quickly escalate into costly gearcase damage if left unaddressed.
A proper repair requires two steps: first, restoring the damaged threads to their original specification; and second, reinstalling the carrier ring nut with correct factory alignment and torque.
The Yamaha Outboard Gearcase Thread Repair Kit from Buckshot Racing #77 provides all of the tools and hardware needed to perform this service correctly. It is specifically designed for the M119 × 2.0 carrier ring nut threads found on Yamaha V6 outboard lower units.
Applications and Compatibility
This repair kit has been engineered for Yamaha six-cylinder four-stroke outboards that share the large carrier nut thread design:
Yamaha 4.2L SHO V6 – 200, 250, 300 hp models (2009–2025)
Yamaha 3.3L V6 – 225 and 250 hp four-stroke models
Both engine families use a fine-pitch 119 mm × 2.0 carrier ring nut thread in the gear housing. This kit provides a universal repair solution for the most common Yamaha V6 outboards in service today.
Kit Contents
1. Buckshot Racing #77 Thread Chaser
A precision tool steel chaser designed to restore damaged or corroded M119 × 2.0 threads in the lower unit gear housing. Unlike a tap, it reforms and cleans the original thread profile without removing unnecessary material.
2. Thread Chaser / Nut Installer Tool
An OEM-style driver used to both run the thread chaser into the housing and install the carrier ring nut after repair. It ensures the nut starts square, seats fully, and torques to spec. Cross-referenced OEM part numbers include: 90890-06513, 90890-06677, YB-06513-M, YB-06677, YB06513M, YB06677.
3. Spanner Cover Retainer Nut
Replacement nut for Yamaha 200–300 hp four-stroke 4.2L engines, OEM part number 6CB-45384-00-00. A new nut ensures proper clamping force and bearing carrier reliability after repair.
Step-by-Step Repair Instructions
Prepare the Gearcase
Secure the lower unit in a vice with soft jaws.
Clean the carrier nut bore with solvent and compressed air to remove salt, corrosion, or debris.
Align the Thread Chaser
Lightly oil the Buckshot Racing #77 chaser.
Insert it into the bore, ensuring it starts square. Begin by hand for the first half-turn to confirm alignment.
Chase the Threads
Advance the chaser using the installer tool in small turns.
After each half-turn forward, back off slightly to break chips and clear debris.
Continue until the full damaged section has been restored.
Inspect and Clean
Remove the chaser, flush the threads with solvent, and inspect under bright light.
Check that the thread peaks and valleys are smooth and continuous.
Test with the New Nut
Thread the new spanner retainer nut into the housing by hand.
It should engage smoothly for several turns without binding.
Install the Carrier Ring Nut
Use the nut installer tool to seat the new carrier nut fully against the housing shoulder.
Torque to factory specification according to Yamaha’s service manual.
Benefits of a Complete Repair Kit
By combining the chaser, installer, and replacement nut in one package, this kit ensures technicians have everything required for a professional-grade repair. It:
Restores damaged threads without replacing the entire housing
Guarantees correct nut alignment and torque
Prevents recurring damage by replacing worn hardware
Saves downtime by providing all required tools and parts in one kit
Care of the Tools
The Buckshot Racing #77 chaser and installer are made from hardened tool steel for repeated use. After service:
Clean the tools in solvent
Apply light oil to prevent corrosion
Store with protective thread caps to maintain accuracy
Thread damage in Yamaha V6 outboards does not require costly gearcase replacement. The Yamaha Outboard Gearcase Thread Repair Kit combines the Buckshot Racing #77 Thread Chaser, the OEM-style Nut Installer Tool, and a new Spanner Cover Retainer Nut into one complete solution.
Compatible with Yamaha 4.2L SHO 200–300 hp (2009–2025) and 3.3L 225–250 hp four-stroke outboards, this kit restores M119 × 2.0 threads to factory specification and ensures long-term durability of the gearcase assembly.
Contact Mike Hill with any technical questions at +1-714-697-1716 or mike@buckshotracing77.com