SD40

The SD40 introduced the cone clutch that Yanmar also used in the SD50. Yanmar's joint SD40/SD50 service manual gives both a bevel gear set with a cone clutch, a 2.32:1 reduction ahead and astern, and a dry mass of 39 kg (41 kg for the -4T version). Applicable engines in that manual are the 3JH3CE and 4JH3CE, with the SD40-4T behind the turbocharged 4JH3-TCE; the -3/-4 suffix variants differ in the engine they fit, and the 4T variant uses an SAE #4 mounting and a higher 140 Nm torque allowance against 129 Nm. The 3JH3/4JH3 operation manual lists it as an alternative to the SD31.

The manual notes an older SD40 type with a smaller oil capacity. The SD40 was followed by the SD50 when the JH4 engines arrived.