Alternator Drive Belt – Fits Volvo Penta D1-30 & D2-40 Series (Replaces 21951188, 3812159)

$38.50

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This aftermarket Alternator Drive Belt is engineered for Volvo Penta 4-stroke marine diesel engines, including the D1-30A (2005–2006), D1-30B (2006–2008), D1-30F (2008+), and compatible D2-40 Series models. It ensures reliable power transmission from the crankshaft to the alternator and other engine accessories.

It serves as a direct replacement for Volvo Penta part numbers 21951188 and its successor, 3812159.

Installation Loci: Mounts to the engine alternator assembly.
Material: Composed of a durable synthetic rubber composite for longevity.
Design: Features a V-belt design for optimal grip and performance.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number	Notes
Volvo Penta	21951188	Superseded by 3812159
Volvo Penta	3812159	Current replacement number

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Volvo Penta owners: This belt is confirmed to fit D1-30 models A, B, and F. Compatibility for the D2-40 series is widely reported by retailers, but we advise verifying your specific engine's part number before ordering.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Volvo Penta	D1-30A	27.9	4-Stroke	2005–2006	21951188/3812159	Marine diesel engine
Volvo Penta	D1-30B	27.9	4-Stroke	2006–2008	21951188/3812159	Marine diesel engine
Volvo Penta	D1-30F	27.9	4-Stroke	2008+	21951188/3812159	Marine diesel engine
Volvo Penta	D2-40 Series	40	4-Stroke		21951188/3812159	Compatible according to retailer

Technical Specs

Product Type: Alternator Drive Belt
Installation: Engine Alternator
Housing Material: Synthetic Rubber Composite
Weight: 0.5 kg (1.1 lb)
Warranty: 1 year against manufacturing defects
Other Technical Attributes: V-belt design

What’s in the Box

1 x Alternator Drive Belt (21951188/3812159)

Installation Notes

Disconnect the boat's battery terminals to prevent accidental starts.
Locate the alternator and the belt tensioner pulley on your engine.
Loosen the tensioner bolt or pivot bolt to release pressure on the belt.
Carefully slip the old belt off the pulleys. Note the routing path.
Route the new belt onto the pulleys, following the same path as the old one. Ensure it is seated correctly in all grooves.
Apply tension to the belt by adjusting the tensioner. A general rule is about half an inch of deflection with firm thumb pressure.
Tighten all bolts securely.
Reconnect the battery, start the engine, and visually inspect the belt to ensure it is running straight and smoothly.

Troubleshooting & FAQ

How do I know if this belt fits my D2-40 engine?

While this belt is listed as compatible with the D2-40 series, specific model years are not confirmed. The best way to ensure fitment is to visually compare your old belt to our product images and confirm your original part number is 21951188 or 3812159.

What are the signs of a failing alternator belt?

Common signs include high-pitched squealing noises (especially on startup), visible cracks or fraying on the belt, a battery that isn't charging correctly, or dimming lights and electrical issues while the engine is running.

What is the recommended replacement interval?

As a general guideline, marine engine drive belts should be inspected annually and replaced every 3-5 years or as recommended by your engine's manufacturer, even if they don't show visible wear.

Is this a direct replacement for part 21951188?

Yes, this is a direct aftermarket replacement for Volvo Penta part number 21951188, which has been superseded by part number 3812159. This belt replaces both.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost?

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns?

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.

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