Sierra 18-6457 Composite Pulley, Replaces 807757T, for Late Model GM V6 & V8 Engines

The Sierra 18-6457 is a composite pulley engineered for late model GM V6 and V8 engines in MerCruiser sterndrive (I/O) cooling system applications. It has a 3 inch outer diameter and is sized for a 13/16 inch width serpentine belt, making it a direct fit for the serpentine belt drive on these engines. The pulley body is molded from composite material, offering a lightweight alternative to a stamped-steel pulley while standing up to the heat, moisture, and vibration of a marine engine compartment.

This pulley is a replacement part for 807757T and is built to restore proper belt alignment and tension on the accessory drive of applicable GM V6 and V8 marine engines. It is a straightforward swap for a worn, cracked, or wobbling factory pulley, helping keep the serpentine belt tracking correctly and reducing belt slip or premature wear.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-6457
• Product Type: Composite Pulley
• Outer Diameter: 3 inches
• Belt Width Compatibility: 13/16 inch
• Pulley Style: Serpentine
• Engine Application: Late model GM V6 & V8 engines
• Color: White
• Material: Composite
• Weight: 0.12 pounds
• UPC: 808282200527

Fitment

Fits late model GM V6 and V8 engines used in MerCruiser sterndrive (I/O) cooling system applications, using a serpentine belt of 13/16 inch width.

Replaces (OEM)

807757T

Frequently Asked Questions

What engines does the Sierra 18-6457 pulley fit? The Sierra 18-6457 composite pulley fits late model GM V6 and V8 engines used in MerCruiser sterndrive (I/O) cooling system applications.

What belt size does this pulley use? It is sized for a 13/16 inch width serpentine belt, matching the outer diameter and groove profile of the 3 inch pulley.

What is the outer diameter of the 18-6457 pulley? 3 inches, measured across the outside of the composite pulley wheel.

Does the Sierra 18-6457 replace part number 807757T? Yes, part number 18-6457 is a direct replacement for 807757T.

What material is the pulley made of? The pulley body is made of composite material rather than stamped steel, and it is finished in white.

How much does the 18-6457 pulley weigh? It weighs 0.12 pounds.

Is this a genuine Sierra part or an aftermarket copy? Part number 18-6457 is a genuine Sierra composite pulley, sold under the Sierra brand as a replacement for OEM part 807757T.

What is included when I order the 18-6457? The order includes one Sierra 18-6457 composite pulley; no mounting hardware or belt is included.

Will this pulley work on a non-GM engine? The 18-6457 is designated for late model GM V6 and V8 engines; fitment on other engine families is not specified for this part.

What system is this pulley used on? The Sierra 18-6457 is used on the serpentine belt drive of the cooling system on applicable MerCruiser I/O engines.