V-Belt for MerCruiser 4.3L, 5.0L & 5.7L Engines – Replaces 57-48120, 57-48120A1, 57-48120Q1
V-Belt for MerCruiser 4.3L, 5.0L & 5.7L Engines – Replaces 57-48120, 57-48120A1, 57-48120Q1 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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V-Belt for MerCruiser 4.3L, 5.0L & 5.7L Engines – Replaces 57-4...
V-Belt for MerCruiser 4.3L, 5.0L & 5.7L Engines – Replaces 57-48120, 57-48120A1, 57-48120Q1 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket V-belt is listed for selected MerCruiser stern-drive and out-drive applications using 4.3L, 5.0L, and 5.7L engines. It is also listed for selected Volvo Penta diesel and OMC Cobra stern-drive applications. The belt is supplied as a single replacement belt, not as a kit.
The company catalog lists this belt as a 46-length V-belt and identifies the following manufacturer and aftermarket reference numbers. Always compare the number on your existing belt and confirm the complete engine application before ordering.
- Product type: Marine V-belt
- Application: Stern-drive and out-drive engine accessory drive
- Listed belt length: 46
- Package type: Single replacement belt
- Aftermarket references: Sierra 18-15460; Mallory Marine 9-55002
Part Number Matrix
The following references are listed for this belt. They are provided for identification and cross-reference purposes only; verify the application and belt dimensions before installation.
| Brand or source | Reference numbers |
|---|---|
| MerCruiser | 57-48120, 57-48120A1, 57-48120Q1, 48120, 48120A1, 48120Q1 |
| Volvo Penta | 829207, 950818, 958316, 966920 |
| OMC Cobra | 0310953, 0509293, 0909971, 310953, 509293, 909971 |
| Sierra Marine | 18-15460 |
| Mallory Marine | 9-55002 |
Engine & Model Compatibility
Fitment below follows the company catalog entries for this belt. Engine model, accessories, power-steering configuration, and production details must be checked together.
MerCruiser Stern-Drive and Out-Drive Applications
| Brand | Engine application | Reference numbers | Application notes |
|---|---|---|---|
| MerCruiser | 4.3L | 57-48120, 57-48120A1, 57-48120Q1, 48120, 48120A1, 48120Q1 | Catalog-listed MerCruiser stern-drive/out-drive application |
| MerCruiser | 5.0L | 57-48120, 57-48120A1, 57-48120Q1, 48120, 48120A1, 48120Q1 | Catalog-listed MerCruiser stern-drive/out-drive application |
| MerCruiser | 5.7L | 57-48120, 57-48120A1, 57-48120Q1, 48120, 48120A1, 48120Q1 | Catalog-listed MerCruiser stern-drive/out-drive application |
Volvo Penta Diesel Applications
| Brand | Engine model | Accessory application | Reference numbers |
|---|---|---|---|
| Volvo Penta | MD21A | Water pump and alternator | 829207 |
| Volvo Penta | MD21B | Water pump and alternator | 829207 |
| Volvo Penta | AQD21A / AQD21B | Listed with the MD21A/MD21B application | 829207, 950818, 958316, 966920 |
OMC Cobra Stern-Drive Applications
| Engine application | Year or condition listed | Accessory configuration | Reference number |
|---|---|---|---|
| 140 | All listed | Water pump and alternator | 310953 |
| 185 | 1978–1984 | Water pump, alternator, and drive-hydraulic power steering configurations as catalog-listed | 909971 |
| 200 | 1979–1981 | Water pump, alternator, and drive-hydraulic power steering configurations as catalog-listed | 909971 |
| 230 / 260 | 1979–1981 | Water pump, alternator, and drive-hydraulic power steering configurations as catalog-listed | 909971 |
| 2.5L | 1982–1987 | Drive-hydraulic power steering configuration | 909971 |
| 3.0L 181 | 1982–1989 | Drive-hydraulic power steering configuration | 909971 |
| 7.5L V-8 460 | From 1987 | Water pump and alternator | 909971 |
Technical Specs
- Product type
- Marine V-belt
- Installation location
- External engine accessory drive
- Listed length
- 46
- Application
- Selected MerCruiser, Volvo Penta, and OMC stern-drive/out-drive applications
- Package format
- Single belt
What’s in the Box
- 1 x marine V-belt
Installation Notes
- Disconnect the battery and make sure the engine cannot start before servicing the belt.
- Confirm the replacement belt reference and inspect the existing belt routing.
- Release the appropriate belt tension by loosening the adjustment mechanism or accessory bracket.
- Remove the old belt and inspect the pulleys for wear, damage, contamination, and misalignment.
- Install the new belt following the engine manufacturer’s routing diagram.
- Adjust belt tension according to the engine service manual. Do not rely on a generic deflection measurement when the manufacturer specifies another procedure.
- Tighten the adjustment and mounting hardware, then recheck belt alignment and tension.
- Reconnect the battery and run the engine briefly while checking belt tracking. Stop immediately if the belt slips, walks off a pulley, or produces abnormal noise.
Troubleshooting & FAQ
How do I know if my V-belt is worn?
Inspect for cracking, glazing, fraying, abnormal wear, contamination, or loss of tension. Squealing or belt movement during operation can also indicate slipping, incorrect tension, pulley misalignment, or a worn pulley.
Does this belt fit every MerCruiser 4.3L, 5.0L, or 5.7L engine?
No. The company catalog lists the belt for these engine sizes, but accessory configuration and engine-specific changes can affect fit. Match the reference number and belt dimensions with your existing belt and service information before ordering.
Is the OMC 7.5L V-8 460 application for every year?
The company catalog specifically lists the OMC 7.5L V-8 460 application from 1987. Earlier or otherwise different configurations should not be assumed to fit without matching the reference number and belt routing.
Does this listing include a pulley, tensioner, or additional hardware?
No. This listing is for one replacement V-belt only.
Can I use this belt on a non-marine engine?
This product is catalog-listed for marine stern-drive and out-drive applications. Do not assume fitment on a non-marine engine solely because the belt appears physically similar.
What should I verify before ordering?
Verify the engine brand, model, displacement, stern-drive or out-drive configuration, accessory arrangement, belt routing, and the reference number from the old belt or service manual. If any of these details differ, confirm compatibility before purchase.
Safety & Important Information
- Work only with the engine stopped, cool, and secured against accidental starting.
- Verify the belt reference, dimensions, routing, and tension requirements for the exact engine configuration.
- Do not operate the engine if the belt is misaligned, loose, damaged, or contacting nearby components.
- This is an aftermarket replacement belt and is not represented as an original manufacturer part.
About Sea Sierra
We provide marine replacement parts and application information to help you identify the correct service component. Because marine engines can vary by accessory configuration and production change, careful reference-number and application matching is recommended before installation.
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