Serpentine Belt Idler Pulley Set – Fits MerCruiser V6/V8 4.3-6.2L (Replaces 8M6500024, 865598, 864625T)

Serpentine Belt Idler Pulley Set – Fits MerCruiser V6/V8 4.3-6.2L

This serpentine belt idler pulley set is designed for a wide range of MerCruiser V6 and V8 marine engines from 1999 to the present, specifically models equipped with a serpentine belt system and a seawater pump. It is a direct replacement for original equipment parts, ensuring proper fit and function.

This kit provides direct replacements for MerCruiser part numbers 8M6500024, 865598 (smooth pulley), and 864625T (grooved pulley), as well as the Sierra aftermarket kit 18-15100.

• Installation Method: Direct replacement for a straightforward installation.
• Engine Fuel Type: Compatible with gasoline engines.
• Complete Kit: Includes both the smooth and grooved idler pulleys required for a full service.

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 x Serpentine Belt (Replaces 57-865615Q03, 862087A1)
• 1 x Smooth Idler Pulley (Replaces 8M6500024, 865598) - ~3-3/16" diameter
• 1 x Grooved Idler Pulley (Replaces 864625T) - ~4-1/4" diameter

Installation Guide

1. Safety First: Disconnect the boat's battery before beginning work.
2. Relieve Belt Tension: Use a breaker bar or serpentine belt tool on the tensioner pulley to release tension from the belt.
3. Remove Old Belt: Carefully slide the old serpentine belt off the pulleys.
4. Remove Old Pulleys: Unbolt and remove both the old smooth and grooved idler pulleys. Note their locations.
5. Install New Pulleys: Mount the new grooved and smooth pulleys in their correct positions and tighten the bolts to the manufacturer's recommended torque specification.
6. Route New Belt: Following the engine's belt diagram, route the new serpentine belt around all pulleys.
7. Apply Tension: Slowly release the tensioner to apply pressure to the new belt, ensuring it is properly seated in all pulley grooves.
8. Final Check: Reconnect the battery. Start the engine and visually inspect the belt and pulleys to ensure they are running smoothly and quietly.

Troubleshooting & FAQ

Q: How do I know if this pulley set will fit my MerCruiser engine?

A: This set is designed for MerCruiser V6 and V8 engines (4.3L, 5.0L, 5.7L, 6.2L, 6.3L) from 1999 to present that use a serpentine belt and a seawater pump. To guarantee fitment, please check your engine model against the "Compatible Engine Models" table and confirm your OEM part numbers match 8M6500024, 865598, or 864625T.

Q: What are the signs that my idler pulleys need replacement?

A: Common signs of failing idler pulleys include a persistent squealing, chirping, or grinding noise from the engine bay, especially when the engine is running. You may also notice visible wobble in a pulley or find cracks or chips on the pulley surface. A worn pulley can lead to belt slippage or complete failure.

Q: Is there a difference between the smooth and grooved pulley in this kit?

A: Yes, they perform different roles. The grooved pulley is designed to guide the ribbed side of the serpentine belt. The smooth pulley runs along the flat, back side of the belt. This kit includes both distinct pulleys for a complete and correct service.

Q: OEM vs. Aftermarket?

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.