Yamaha 15HP Forward Gear: Independent Carburizing Hardness & Metallographic Report

At Ningbo Gill Transmission Parts Co., Ltd., we know that outboard motor gears face constant high torque, vibration, and saltwater corrosion. Insufficient surface hardness or poor case depth often leads to rapid wear or failure in real-world marine use.

To ensure reliability, we conduct regular third-party testing on key components, such as our Yamaha 15HP forward gears.

The latest report from an independent lab (dated January 17, 2026) tested a carburized and quenched batch of 20CrMo steel gears. Results confirm excellent performance:

Surface Hardness (HRA): Measured values 80.5–81.0 (specification HRA80-82) – fully compliant.

Effective Case Depth: 0.54 mm (specification 0.4–0.6 mm) – within range, ensuring strong wear resistance.

Hardness Gradient (HV1.0): From 706 HV at 0.1 mm to 486 HV at 0.6 mm – smooth transition, no defects.

Metallographic Structure: Martensite + retained austenite + carbide Grade 1 (per QC/T 262-1999) – fine and uniform microstructure.

These results prove our gears achieve deep, hard surface layers for superior durability in high-load conditions, reducing the risk of early failure compared to lower-quality alternatives.We believe transparency builds trust.