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Yanmar Gearbox

KM4A

Kanzaki-built 7-degree down-angle cone-clutch gear with 1.47, 2.14 or 2.63:1 ratios for the 4JH engines, sold as KM4A1 (SAE #5, naturally aspirated) and KM4A2 (SAE #4, turbo).

The KM4A is a mechanical servo cone-clutch gear with a 7-degree down-angle output and equal ahead and astern ratios, available in either propeller rotation. Kanzaki's current KM4A-2 is rated at 241 Nm input at 3,200 rpm with ratios of 1.47, 2.14 and 2.63:1 and a dry weight of 28.5 kg on an SAE #4 flange. Yanmar's 2020 gear table lists the KM4A1-5 for the 4JH5E, 4JH45 and 4JH57 (28 kg) and the KM4A2-4 for the 4JH4-TE, 4JH4-HTE, 4JH80 and 4JH110 (30 kg).

The 3JH3/4JH3 operation manual lists the KM4A1 for the 4JH3E with 2.14, 2.63 and 3.30:1 ratios. Kanzaki's 1998 service manual already covers a KM4A, and Yanmar's parts catalogue has separate books for the KM4A, KM4A1 and KM4A2. It remains current.

Sources

  1. 1. KM4A-2 marine gear — Kanzaki Kokyukoki Mfg. Co., Ltd.
  2. 2. Kanzaki Gears product page with gear/engine applicability table (2020 capture) — Yanmar Marine International
  3. 3. Operation Manual 3JH3(B)E, 3JH3(C)E, 4JH3(B)E, 4JH3(C)E — Yanmar
  4. 4. JH Series Operation Manual 4JH45, 4JH57, 4JH80, 4JH110 (0AJHC-M00011, 2014) — Yanmar
  5. 5. Kanzaki Marine Gear Manuals (manual index) — Marine Diesel Basics
  6. 6. Yanmar Marine parts catalogue: Clutch, KM Series — Yanmar Shop (Yanmar parts data)

Specifications compiled from manufacturer sources.