Volvo Penta Multi-Ribbed Drive Belt 21951188 – D1 / D2 Series
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Volvo Penta Multi-Ribbed Drive Belt – Part No. 21951188
Part Number: 21951188
Brand: Volvo Penta
Supersedes: 3812159
Replaced By: Current – 21951188 is the active OEM number
Overview
This is a genuine Volvo Penta OEM multi-ribbed (serpentine) drive belt for D1 and D2 series marine diesel engines. It transfers power from the engine crankshaft to the alternator and cooling system components, keeping the charging and cooling circuits running reliably. As an OEM belt, it matches the original rib count, length, and material specification required for proper tension and accessory drive performance in the marine environment.
System
Accessory Drive System – Alternator and Cooling Circuit. This belt drives the alternator and water pump on the applicable D1/D2 engine configurations.
Compatible Applications
- Volvo Penta D1-13 (B and F variants)
- Volvo Penta D1-20 (B and F variants)
- Volvo Penta D1-30 (B and F variants)
- Volvo Penta D2-40 (B and F variants)
- Other Volvo Penta D1/D2 series engines where the accessory drive diagram calls for part number 21951188 – confirm by engine serial number
Serial Number & Fitment Notice
Accessory belt configurations can vary by engine model, production run, and alternator or pump specification. Always confirm part number 21951188 against your engine serial number and the correct Volvo Penta accessory drive diagram before ordering.
Superseded Part Numbers
Earlier part number 3812159 has been updated to 21951188. Use 21951188 as the current OEM ordering number.
Service Interval
Volvo Penta recommends inspecting the drive belt at every annual service. Replace the belt at the first sign of cracking, glazing, fraying, rib wear, or loss of tension — or at a minimum every 2 years / 300 hours, whichever comes first. Always replace the belt if it has been removed during other service work, as reinstalled belts can lose tension set.
When to Replace
Replace this belt when you notice squealing or chirping from the accessory drive, visible cracking or glazing on the ribs, fraying at the belt edges, alternator undercharging, or overheating caused by reduced water pump speed. A belt that has been in service for more than two seasons should be inspected carefully even if it looks intact.
Installation Notes
Check belt tension after installation and re-check after the first hour of operation — new belts seat and can lose tension quickly. Inspect the alternator and water pump pulleys for wear, misalignment, or bearing play at the same time. A worn pulley will shorten belt life significantly.
Technical FAQ
Q: Can I use an aftermarket belt instead of OEM?
A: Aftermarket belts with matching dimensions may fit, but rib profile and material grade vary between suppliers. An OEM belt ensures the correct load rating and flex characteristics for the D1/D2 accessory drive layout.
Q: How do I know if my belt is the right tension?
A: Refer to the Volvo Penta service manual for the D1 or D2 engine. Tension is typically checked by deflection at the midpoint of the longest belt span. A belt that is too loose will slip; too tight will accelerate bearing wear on the alternator and water pump.
Q: My alternator is not charging — is the belt the cause?
A: A slipping or broken drive belt is one of the first things to check. If the belt is intact and tensioned correctly, the issue is more likely the alternator itself or the charging circuit.
Parts Desk Insights
This belt is one of the most straightforward annual service items on the D1 and D2 engine family — inexpensive, quick to replace, and easy to overlook until it fails. The most common issue is skipping belt replacement during a service because the belt looks fine visually. Rib cracking on multi-ribbed belts often starts on the inner surface and is not visible without flexing the belt. If the engine has more than two seasons on the original belt, replace it as a matter of course rather than waiting for a symptom.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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