807757 Serpentine Belt Idler Pulley for Mercruiser GM V6 V8 | JLM Marine

Serpentine Belt Idler Pulley – Fits Mercruiser Late Model GM V-6 & V-8 Engines

This serpentine belt idler pulley is engineered for Mercruiser late model GM V-6 and V-8 engines, providing reliable tensioning and smooth belt operation. Built to meet OEM specifications, this aftermarket replacement ensures consistent performance in your marine drivetrain.

Direct Replacements: Mercury MerCruiser Marine 807757T, 807757 | Sierra Marine 18-6457

• 3-inch diameter pulley with six grooves for proper belt alignment
• Designed for late model GM V-6 & V-8 Mercruiser applications
• Precision-manufactured for long-lasting durability

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 1 × Serpentine Belt Idler Pulley (3" diameter, 6 grooves)

Installation Guide

1. Disconnect the battery negative terminal to ensure electrical safety during installation.
2. Release tension on the serpentine belt using the appropriate tensioner tool and remove the belt from the pulleys.
3. Locate the idler pulley mounted on the engine block or accessory bracket.
4. Remove the mounting bolt securing the old idler pulley using the correct socket wrench. Keep the hardware for reuse if in good condition.
5. Inspect the mounting surface for debris, corrosion, or damage and clean if necessary.
6. Position the new idler pulley onto the mounting bracket, aligning the bolt hole properly.
7. Insert and hand-tighten the mounting bolt, then torque to manufacturer specifications (refer to your engine manual for proper torque values).
8. Route the serpentine belt around all pulleys following the belt routing diagram for your specific engine model.
9. Use the tensioner to apply proper tension and seat the belt into all six grooves of the new idler pulley.
10. Verify that the belt is correctly seated on all pulleys and aligned without twisting or misalignment.
11. Reconnect the battery negative terminal and start the engine to check for proper operation.
12. Inspect for unusual noise, vibration, or belt slip; adjust tension or alignment if needed.

Troubleshooting & FAQ

Q: How do I confirm this idler pulley fits my Mercruiser engine?
A: Verify your engine is a late model GM V-6 or V-8 Mercruiser. Cross-reference the OEM part number 807757 or 807757T with your service manual or parts diagram to ensure compatibility.

Q: What are the signs that my idler pulley needs replacement?
A: Common symptoms include squealing or chirping noises from the belt area, visible wobble or play in the pulley, belt wear or fraying, and overheating of accessories due to improper belt tension.

Q: How often should I replace the serpentine belt idler pulley?
A: Inspect the idler pulley annually or every 100 hours of operation. Replace it if you notice bearing noise, roughness when spinning, or whenever replacing the serpentine belt as preventive maintenance.

Q: Can I reuse the original mounting bolt?
A: Yes, you can reuse the original mounting bolt if it shows no signs of damage, corrosion, or stripped threads. Always torque to manufacturer specifications for secure installation.

Q: What's the difference between this aftermarket pulley and the OEM version?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.