Balmar 120A Saddle Mount Alternator, 4-Inch K6 Pulley

Description

The Balmar 604 Series 120A Saddle Mount Alternator provides high-output 12V charging for larger marine engines using a 4-inch J-180-style dual-foot mount. Its K6 serpentine pulley and isolated-ground electrical configuration make it suitable for charging-system upgrades where the engine already uses or is being converted to a compatible six-rib belt drive.

The 4-inch J-180 mounting pattern is typical of Caterpillar, Cummins, Detroit Diesel, and John Deere engines. Matching the mount width, pivot hardware, pulley alignment, and belt system before installation is important because this larger saddle configuration differs from the 3.15-inch mounts commonly used on smaller marine diesels.

The alternator is rated for 120 amps at 12V, providing increased charging capability for larger house banks, inverter-equipped boats, and vessels with substantial continuous electrical loads. Isolated grounding separates the alternator’s electrical ground path from the case, which can be important in specific marine electrical-system designs.

This listing is for the alternator rather than a complete regulator and temperature-sensor kit, so compatible regulation and charging-system wiring must be provided separately. The unit replaces Balmar 604-120-SR-IG. For large-engine installations requiring a 4-inch J-180 mount, K6 pulley, isolated ground, and 120A output, this Balmar alternator provides a purpose-built marine charging upgrade. Worth comparing against our other marine alternators.