Yanmar — V-belt tension check and adjustment
Maintenance · V-belt / alternator
From a Yanmar service manual — check it applies to your exact model before use.
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Before you start
- Be careful not to splash engine oil on the V-belt; it causes slipping, stretching and aging
Procedure
- Press the V-belt with your thumb approx 98N (10kgf) at middle of span
- Check the tension (deflection) at A, B or C direction
- Loosen the set bolt and move the alternator to adjust V-belt tension
- After replacing with a new V-belt, run engine 5 minutes and readjust deflection
- Visually check V-belt for cracks, oiliness or wear; replace if present
Tools required
- Bar for adjusting V-belt tension Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Direction A: used 10~14 mm, new 8~12 mm
- Direction B: used 7~10 mm, new 5~8 mm
- Direction C: used 9~13 mm, new 7~11 mm
Source: Yanmar service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.