Alternator V-belt Yanmar 1GMY-C | 1GMY-EC – HM33 (837 mm)

Description

Replacement alternator belt for the Yanmar 1GMY-C and 1GMY-EC — the single-cylinder sailboat engines from the GM family. This belt runs from the crankshaft pulley to the alternator and is the only belt on this engine.

Yanmar specifies belts as a profile letter plus nominal length in inches. HM33 therefore stands for a 10 mm narrow wedge profile of 33 inches, or approximately 837 mm.

✔️ The size specified by Yanmar in the parts catalog for the 1GMY-C and 1GMY-EC
✔️ Narrow wedge profile 10 x 6 mm, like the original version
✔️ For a classic engine with limited availability

Dimensions

• Designation: HM33
• Profile: 10 x 6 mm
• Length: approx. 837 mm (33 inch nominal)

Belt lengths are specified in various ways: Li is the inside circumference, Lw/Ld is the pitch length, and La is the outside circumference. When in doubt, measure your old belt.

Suitable for

• Yanmar: 1GMY-C, 1GMY-EC

Please note

• Yanmar used two different belt lengths for the 1GMY — this HM33 and the shorter HM31 (approx. 790 mm), depending on the fitted alternator. Measure your old belt or check which alternator is installed on your engine before ordering.
• The 1GMY does not have a raw water pump belt. On this single-cylinder engine, the raw water pump is driven by gears from the camshaft.
• Do not confuse this number with 104514-77350: that is the shorter HM23 of approx. 584 mm.

Maintenance

Check the belt tension every 250 operating hours and replace the belt if you notice cracks, fraying, or a glazed flank. Having a spare belt on board is a must on a single-cylinder engine — without an alternator belt, the battery will no longer charge.

OEM for reference

• 104514-42780
• 10451442780
• 25137-003300 (replacement number according to the Yanmar dealer catalog)
• 25137003300