Sierra Serpentine Belt 18-15115, OEM 57-861757/57-861757Q, 13/16 Inch x 97.5 Inch, MerCruiser

The Sierra 18-15115 is a serpentine belt engineered for MerCruiser serpentine-drive applications, built to OEM quality standards for correct fit, form, and function. It measures 13/16 inch wide by 97.5 inches long, matching the exact dimensions of the OEM belt it replaces so pulley alignment and tensioner geometry stay correct. The belt is constructed from polyester and rubber, using polychloroprene rubber compounded with polyester fiber tensile members that give the belt oil resistance and temperature stability for continuous duty in a marine engine bay. Serpentine belts drive multiple engine accessories (such as the alternator, water pump, and power steering pump where equipped) from a single continuous-loop belt routed around the engine's pulley system, so a correctly sized, durable belt is essential to reliable charging and cooling. This belt is cross-referenced to the OEM numbers 57-861757 and 57-861757Q, making it a direct fit replacement for engines originally equipped with either of those belts. Each belt ships as a single unit ready to install using the engine's existing tensioner.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-15115
• OEM Cross-Reference: 57-861757, 57-861757Q
• Belt Style: Serpentine
• Width: 13/16 inch
• Length: 97.5 inches
• Material: Polyester, Rubber
• Weight: 0.55 pounds
• UPC: 808282145491
• Country of Origin: United States

Fitment

Sierra 18-15115 is identified by its own part number for MerCruiser serpentine belt applications; confirm fitment against the OEM numbers below or against part number 18-15115 directly.

Replaces (OEM)

• 57-861757
• 57-861757Q

Frequently Asked Questions

What size is the Sierra 18-15115 serpentine belt? It measures 13/16 inch wide by 97.5 inches long, the exact dimensions needed for a correct OEM-matching fit.

What OEM part numbers does 18-15115 replace? Part number 18-15115 cross-references to OEM numbers 57-861757 and 57-861757Q, so either original belt can be replaced with this one.

What material is this belt made from? The belt is made from polyester and rubber, using polychloroprene rubber combined with polyester fiber tensile members for strength and heat resistance.

Is the Sierra 18-15115 belt oil and heat resistant? Yes, oil resistance and temperature stability are standard features of this belt's construction, which suits the engine-bay environment it operates in.

Is this a genuine OEM belt or an aftermarket replacement? The 18-15115 is a Sierra aftermarket belt engineered to OEM quality standards for fit, form, and function, not a manufacturer-branded original part.

What does 'serpentine belt' mean for this application? A serpentine belt is a single continuous-loop belt, like the Sierra 18-15115, that drives multiple engine accessories from one belt routed around the engine's pulleys.

What is included when I order part number 18-15115? One serpentine belt, part number 18-15115, ships as a single unit ready to install with the engine's existing tensioner.

Will this belt fit any engine that uses a 13/16 by 97.5 inch belt? Sierra 18-15115 is sized 13/16 inch wide and 97.5 inches long, so it fits engines specified for that belt length and width or for OEM numbers 57-861757 or 57-861757Q.

How do I know if I need 18-15115 versus a different Sierra belt number? Match the belt by its length and OEM cross-reference; 18-15115 is 97.5 inches long, while other Sierra part numbers in the same line cover different lengths, so confirm against your original belt's OEM number, 57-861757 or 57-861757Q.

What is the weight of the 18-15115 belt? The Sierra 18-15115 serpentine belt weighs 0.55 pounds.