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

The Balmar 604 Series 120A Saddle Mount Alternator has a K6 pulley and isolated ground, for 4-inch J-180-style dual-foot mounts.

Four-inch J-180 is a larger mounting pattern than the 3.15-inch saddles, and it appears on commercial-grade engines. Caterpillar, Cummins, Detroit Diesel and John Deere use it, so this is the alternator for a larger vessel rather than a recreational auxiliary.

Mount width, pivot hardware, pulley alignment and belt system all need checking together before installation. Getting the mount right but the alignment wrong throws the belt off true, and a misaligned serpentine belt destroys itself quickly rather than merely wearing.

Isolated-ground construction keeps the charging return in a dedicated cable rather than through the engine block. The K6 six-groove serpentine pulley must match the existing belt, and this is the alternator alone rather than a kit. Explore more marine alternators.

• 4-inch J-180, larger than the 3.15-inch saddles
• Found on Caterpillar, Cummins and Detroit Diesel
• Check mount, pivot, alignment and belt together
• A misaligned serpentine belt destroys itself quickly