Serpentine Belt for MerCruiser Alpha 4.3L, 5.0L, 5.7L and 350 Mag Engines – Sierra 18-15116
Serpentine Belt for MerCruiser Alpha 4.3L, 5.0L, 5.7L and 350 Mag Engines – Sierra 18-15116 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Serpentine Belt for MerCruiser Alpha 4.3L, 5.0L, 5.7L and 350 Mag E...
Serpentine Belt for MerCruiser Alpha 4.3L, 5.0L, 5.7L and 350 Mag Engines – Sierra 18-15116 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket serpentine belt is designed for specified MerCruiser Alpha applications, including 4.3L, 5.0L, 5.7L and 350 Mag engines. It is listed as Sierra 18-15116 and cross-referenced to MerCruiser belt numbers 57-861758 and 57-861758Q. The belt is used with the applicable accessory-drive arrangement and is intended for engines equipped with a metal 5-3/4-inch power-steering pump pulley and standard cooling where noted by the application.
Always match the complete engine model, year and serial-number range before ordering. Belt applications can vary by engine family, cooling configuration, pulley arrangement and accessory layout.
- Ribbed serpentine belt for the MerCruiser accessory drive.
- Listed for selected MerCruiser Alpha and 350 Mag Alpha applications.
- Application-specific fitment includes the engine serial ranges shown below.
- Aftermarket replacement for the listed MerCruiser belt references; not a genuine MerCruiser-branded part.
Part Number Matrix
The following numbers are the documented product and manufacturer cross-references for this belt.
| Brand or source | Part Number |
|---|---|
| Sierra | 18-15116 |
| MerCruiser | 57-861758 |
| MerCruiser | 57-861758Q |
| MerCruiser | 861758A1 |
| MerCruiser | 861758Q |
| MerCruiser | 8M0150824 |
Engine & Model Compatibility
Use the engine model, production year and serial number together when confirming fitment. The listed applications use serpentine belt 18-15116 / MerCruiser reference 57-861758.
| Brand | Model | Years | Serial-number range | Belt reference | Application notes |
|---|---|---|---|---|---|
| MerCruiser | 4.3L Alpha | 1996–1999 | OF803000–OL618999 | 18-15116 / 57-861758 | Metal 5-3/4-inch power-steering pump pulley; standard cooling application. |
| MerCruiser | 5.0L Alpha | 1998–1999 | OL012052–OL618999 | 18-15116 / 57-861758 | Metal 5-3/4-inch power-steering pump pulley; standard cooling application. |
| MerCruiser | 5.7L Alpha | 1997–1999 | OK001501–OL618999 | 18-15116 / 57-861758 | Metal 5-3/4-inch power-steering pump pulley; standard cooling application. |
| MerCruiser | 350 Mag Alpha | 1997–2004 | OK001501–OL618999 | 18-15116 / 57-861758 | Confirm the pulley, cooling-system and accessory configuration before purchase. |
Technical Specs
- Product Type
- Marine serpentine belt
- Application
- MerCruiser stern-drive / out-drive accessory drive
- Belt Type
- Ribbed serpentine belt
- Listed Belt Length
- 86.75 inches
- Listed Belt Width
- 13/16 inch
- Application Configuration
- Metal 5-3/4-inch power-steering pump pulley and standard cooling where specified
- Color
- Black
- Aftermarket Reference
- Sierra 18-15116
- MerCruiser References
- 57-861758, 57-861758Q, 861758A1, 861758Q and 8M0150824
What’s in the Box
- 1 x Serpentine belt
Installation Notes
- Confirm the engine model, year, serial number and accessory configuration before installation.
- Turn the engine off, allow it to cool completely and disconnect the negative battery cable.
- Photograph or document the existing belt-routing path before removing the old belt.
- Release the belt tensioner or accessory adjustment as required by the specific engine configuration.
- Remove the old belt and inspect the pulleys for wobble, damage, corrosion, contamination or damaged grooves.
- Route the replacement belt around the pulleys according to the engine service information. Make sure every rib is fully seated.
- Restore the specified belt tension and rotate the engine by hand, where appropriate, to verify correct tracking.
- Reconnect the battery, start the engine and observe the belt briefly for tracking, noise or slippage. Stop the engine immediately if the belt does not run correctly.
Troubleshooting & FAQ
How do I confirm that this belt fits my engine?
Match your MerCruiser engine model, year and complete serial-number range to the compatibility table. Also verify the pulley and cooling-system configuration. If any of these details differ, consult the engine service information before ordering.
Which belt references does this part replace?
This aftermarket belt is listed as Sierra 18-15116 and cross-referenced to MerCruiser numbers 57-861758 and 57-861758Q. Additional documented MerCruiser references include 861758A1, 861758Q and 8M0150824.
What are signs that the serpentine belt needs replacement?
Inspect the belt for cracking, fraying, glazing, missing ribs, contamination or abnormal wear. Squealing, chirping, poor accessory operation or visible belt misalignment can also indicate a belt, pulley or tension problem.
Does this belt fit later MerCruiser Alpha engines?
Not necessarily. The listed 4.3L, 5.0L and 5.7L Alpha applications are limited to the years and serial ranges shown. Later engines may use different belt references, so do not rely on engine displacement alone.
Is this an OEM MerCruiser belt?
No. This is an aftermarket replacement belt listed against the MerCruiser references shown above. MerCruiser and related manufacturer names and part numbers are used only to identify application and cross-reference information.
Can I use this belt with modified accessories?
Modified accessory drives, different pulleys, high-output alternators or other non-standard equipment may require a different belt length or configuration. Verify the complete drive arrangement before installation.
How often should a marine serpentine belt be inspected?
Inspect the belt during regular maintenance and before extended operation. Follow the engine manufacturer's service information for replacement intervals and inspect more frequently in severe, wet or contaminated operating conditions.
Shipping speed and cost?
Typical transit is 5–15 days depending on destination and service selected. Available shipping methods and costs are shown at checkout.
Warranty and returns?
Returns and any applicable warranty are handled according to the current store policy. Contact support with your order details if you need assistance.
Safety & Important Information
- Do not work on a running engine or attempt belt removal while components are hot or moving.
- Verify the model, year, serial number, pulley arrangement and cooling configuration before purchase.
- Do not install a belt that is contaminated, damaged or incorrectly sized.
- This is an aftermarket replacement, not a genuine MerCruiser-branded component.
- Professional installation is recommended if the correct routing or tension procedure is uncertain.
About Sea Sierra
- Marine-Focused Parts — We supply replacement components for marine propulsion and accessory systems.
- Application-Conscious Listings — Fitment information is organized around model, year and serial-number conditions where available.
- Global Fulfillment — Standard and expedited shipping options are displayed at checkout where available.
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