Belt Tensioner Pulley – Fits MerCruiser 4.3-8.1L Engines

Belt Tensioner Pulley – Fits MerCruiser 4.3-8.1L Engines (Replaces 8M6500024, 865598)

This belt tensioner pulley is designed for a wide range of MerCruiser inboard and stern drive engines, including 4.3L, 5.0L, 5.7L, 5.8L, 6.2L, and 8.1L V6/V8 models from 1996–2025. It is also compatible with General Motors 262 CID V6 (4.3L) and GM V8 small block 5.0L & 5.7L engine blocks.

This is a direct replacement for Mercury part numbers 8M6500024, 818382, and 865598. It also replaces aftermarket parts from Sierra, Heurofosh, and YiheoZux.

• Installation Method: Direct replacement
• Pulley Type: Smooth, flat surface (no grooves)
• Housing Material: High-strength thermal resin

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.

Confirm your engine model/year in the table below.

MerCruiser/Mercury

General Motors

Technical Specifications

Package Contents

• 1 x Belt Tensioner Pulley (8M6500024/865598/818382)

Installation Guide

Always consult your engine’s service manual before beginning work. The general steps for replacement are as follows:

1. Disconnect the Battery: Ensure the engine is off and disconnect the negative battery terminal for safety.
2. Locate the Tensioner Assembly: Find the serpentine belt and trace it to the spring-loaded tensioner assembly where the pulley is mounted.
3. Release Belt Tension: Use a socket wrench or serpentine belt tool on the tensioner arm bolt to release tension and carefully slip the belt off the pulley.
4. Remove the Old Pulley: Unbolt the center bolt holding the old pulley to the tensioner arm and remove it.
5. Install the New Pulley: Position the new pulley, ensuring it is correctly aligned, and tighten the center bolt to the manufacturer's specified torque.
6. Reinstall the Serpentine Belt: Route the belt correctly around all pulleys according to your engine's diagram. Release the tensioner arm to tighten the belt.
7. Final Check: Reconnect the battery terminal. Start the engine and listen for any unusual noises and visually confirm the belt is tracking correctly on the new pulley.

Troubleshooting & FAQ

Q: How do I confirm this fits my engine?
A: The most reliable method is to match your existing part number to those listed in our Part Number Cross-Reference table. Additionally, check your engine model and year against the Compatible Engine Models list. Visual comparison with our product photos is also recommended.

Q: What are the common signs of a failing tensioner pulley?
A: Symptoms of a bad pulley include a persistent squealing or grinding noise from the engine bay, visible wobbling of the pulley while the engine is running, and premature or uneven wear on the serpentine belt.

Q: What is the difference between this and the OEM part?
A: This is an aftermarket pulley made from high-strength thermal resin, similar to the original. The bearing is molded directly into the pulley for durability. It is designed to meet or exceed OEM specifications for fit and performance.

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.