# 21727737 Alternator | Genuine Volvo Penta Part

## 🔧 Product Description

A genuine heavy-duty three-phase alternator used on selected Volvo Penta industrial and marine diesel engines. It supplies regulated charging current for the battery bank and engine electrical loads.

## 🚤 Compatibility

-   **HP Range:** Approximately 250-400 HP
-   **Year Range:** Approximately 2010 - 2021

## ⚙️ Key Features

-   Heavy-duty three-phase alternator construction
-   Integrated or matched voltage regulation
-   Industrial-engine heat and vibration resistance
-   Factory mounting and pulley alignment
-   Direct replacement for the specified charging system
-   Engine type: 7.7L inline six-cylinder turbocharged industrial diesel
-   Also supersedes Volvo part numbers 3090430 and 3803573

## 🔌 Function

An engine-driven charging unit that converts mechanical rotation into regulated electrical power for the batteries and electrical system.

## ⚠️ Common Signs of Failure

-   Low or high charging voltage
-   Battery warning lamp remains active
-   Bearing noise or pulley wobble
-   Overheated output cable or terminals
-   Intermittent charging as the unit warms

## 🛠️ Service Notes

-   Isolate the batteries before you start, and never disconnect the alternator or battery cables with the engine running — that will destroy the diodes
-   Reconnect exactly as it came off, correct polarity, terminals clean and tight, and check the earth path through the mountings and engine is sound
-   Check the pulleys line up and the belt runs true; renew a glazed, cracked or oil-contaminated belt at the same time and tension it by the procedure in the manual for your engine
-   Support the alternator while you fit and tighten the mounting and adjusting bolts to the manual's figures, and never lever against the alternator body or end covers
-   After fitting, confirm the charge warning goes out and charging voltage is correct, and recheck belt tension after the first running period

## 🔄 Supersession & Cross Reference

### OEM Supersession Chain

-   21727737 → Supersedes 21048177 → Supersedes 21048174 → Supersedes 3986428 → Supersedes 3803574

### OEM / Related Numbers

-   21048177 earlier number superseded by this part
-   3986429 earlier number superseded by this part
-   21048174 earlier number superseded by this part
-   3986428 earlier number superseded by this part
-   3803574 earlier number superseded by this part

## 📦 Condition

-   Genuine Volvo Penta part
-   Brand new
-   Supplied in original or equivalent packaging

## Details

- **Price:** 1662.73 AUD
- **Vendor:** Volvo Penta
- **Type:** Charging & Alternators
- **Tags:** Volvo Penta

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 1662.73 AUD | In stock |

## Images

- 21727737 Alternator | Genuine Volvo Penta Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/21727737-alternator-genuine-volvo-penta)
> Updated: 2026-10-09