Balmar Serpentine Pulley Kit for Yanmar 2GM20, 3GM30

The Balmar AltMount Serpentine Pulley Conversion Kit suits Yanmar 3GM-series diesels, including 3GM30-F and 3GM-F applications.

The 2GM and 3GM engines are small auxiliaries, and that is exactly where a charging upgrade runs into belt limits soonest. A small engine has a small crankshaft pulley, so there is less contact area to work with before a V-belt starts slipping under alternator load.

A wider serpentine belt gives greater pulley contact, reducing slip as charging demand increases. That matters on a cruising boat where the engine runs specifically to charge, since a slipping belt means the alternator never reaches its rated output no matter how long the engine runs.

The kit converts the accessory drive as a set rather than the alternator pulley alone. Converting one pulley in isolation leaves a drive that cannot be belted, so these are supplied as matched sets. Explore more alternator mounts and pulleys.

• Small auxiliaries hit belt limits soonest
• A small crank pulley gives less contact to work with
• A slipping belt means the alternator never reaches its rating
• Supplied as a matched set, not a single pulley