SKU: 36641660560

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

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Description

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

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.

Brand Part Number
MerCruiser 8M6500024
MerCruiser 865598
MerCruiser 864625T
Sierra 18-15100

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.

Brand Model Rated HP Stroke Years OEM Part No. Notes
MerCruiser Alpha/Bravo 4.3L Various 4-Stroke 1999–Present 8M6500024/865598 (smooth)
864625T (grooved)
Models with seawater pump
MerCruiser Alpha/Bravo 5.0L Various 4-Stroke 1999–Present 8M6500024/865598 (smooth)
864625T (grooved)
Models with seawater pump
MerCruiser Alpha/Bravo 5.7L Various 4-Stroke 1999–Present 8M6500024/865598 (smooth)
864625T (grooved)
Models with seawater pump
MerCruiser Alpha/Bravo 6.2L Various 4-Stroke 1999–Present 8M6500024/865598 (smooth)
864625T (grooved)
Models with seawater pump
MerCruiser Alpha/Bravo 6.3L Various 4-Stroke 1999–Present 8M6500024/865598 (smooth)
864625T (grooved)
Models with seawater pump
MerCruiser MPI 4.3-6.2L Various 4-Stroke 1999–Present 8M6500024/865598 (smooth)
864625T (grooved)
Models with seawater pump

Technical Specifications

Specification Value
Product Type Serpentine Belt Idler Pulley Set
Installation Direct replacement
Fuel Type Gasoline
Dimensions Smooth Pulley: ~3-3/16" (81mm) diameter
Grooved Pulley: ~4-1/4" (108mm) diameter
Other Technical Attributes Includes both smooth and grooved pulleys for complete service

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.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 36641660560

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gerald johnson
San Leandro, US
★★★★★ 5
GDI ally.
Number of Items: 1
Seems to be effective at reducing oil consumption issue common in many GDI engines.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 2, 2026
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Lonnie S.
Dallas, US
★★★★★ 5
I would highly recommend this product.
Number of Items: 1
I’m going to purchase this product again. I drive a lot and it’s perfect for me and yes, it does work in my opinion. I noticed a difference right away after the oil change. My vehicle was much smoother.
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Reviewed in the United States on May 15, 2026
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Geoffrey Marsh
Lexington, US
★★★★★ 5
Great for Subaru oil consumption
Number of Items: 1, Number of Items: 1
Got this for my 2015 Subaru outback for its notorious oil consumption. It seems to be doing the trick causing less oil consumption after 1k miles noticable difference for sure.
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Reviewed in the United States on January 4, 2026
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GEORGE A SNARSKI
Waukegan, US
★★★★★ 5
great for any engin
Size: 12 fl. oz. (Pack of 1)
Have been looking for this for a long time.i always used when i had a ,chevy 327,300.3speed.the engin always run great and when we changed the value cover gaskests the inside look like brand new,and clean.
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Reviewed in the United States on May 31, 2026
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Verified Purchase
Citasio
Dallas, US
★★★★★ 5
Great product
Size: 12 fl. oz. (Pack of 1)
Noticeable difference in the first 50 miles .
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Reviewed in the United States on March 30, 2026

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