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 (Replaces 8M6500024, 865598, 864625T) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Serpentine Belt Idler Pulley Set – Fits MerCruiser V6/V8 4.3-6.2L (...
Product Details
This Serpentine Belt Idler Pulley Set is designed for MerCruiser V6 and V8 marine engines (4.3L, 5.0L, 5.7L, 6.2L, 6.3L) from 1999 to present that are equipped with a serpentine belt system and a seawater pump. It provides a reliable, direct-fit solution to restore belt system integrity and performance.
The kit serves as a direct interchange for MerCruiser part numbers 8M6500024 and 865598 (smooth pulley), 864625T (grooved pulley), and the complete Sierra 18-15100 aftermarket kit.
- Engineered for direct-fit installation.
- Kit includes both the smooth and grooved idler pulleys for a complete service.
- Designed for gasoline marine inboard engines.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| MerCruiser | 8M6500024 / 865598 | Smooth Pulley |
| MerCruiser | 864625T | Grooved Pulley |
| Sierra | 18-15100 | Kit |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
MerCruiser: This set fits various Alpha and Bravo models with serpentine belt systems and a seawater pump manufactured from 1999 onwards.
| 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 Specs
- 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
What’s in the Box
- 1 x Serpentine Belt (Replaces 862087A1, 57-862087A1, 57-8638763, 57-865615003, 57-865615Q03)
- 1 x Smooth Idler Pulley (Replaces 8M6500024, 865598) - ~3-3/16" diameter
- 1 x Grooved Idler Pulley (Replaces 864625T) - ~4-1/4" diameter
Installation Notes
- Disconnect the boat's battery for safety.
- Locate the serpentine belt tensioner. Use a breaker bar or appropriate tool to release the tension on the belt.
- Carefully slide the old serpentine belt off the pulleys. Note the routing path before removal.
- Unbolt and remove the old smooth and grooved idler pulleys.
- Install the new idler pulleys, ensuring they are seated correctly. Torque the bolts to the manufacturer's specifications.
- Route the new serpentine belt according to the engine's diagram.
- Re-engage the tensioner to apply proper tension to the new belt.
- Reconnect the battery. Start the engine and check for proper belt alignment and listen for any unusual noises.
Troubleshooting & FAQ
Does this kit include both pulleys?
Yes, this kit is a complete set that includes both the smooth idler pulley and the grooved idler pulley required for a full service on compatible MerCruiser engines.
What are the signs of a failing idler pulley?
Common symptoms include a persistent squealing or chirping noise from the engine bay, a visible wobble in the pulley while the engine is running, or physical damage like cracks or chips on the pulley itself.
Will this fit an engine without a seawater pump?
This kit is specifically designed for MerCruiser models from 1999 to present that are equipped with a serpentine belt system AND a seawater pump. Please verify your engine configuration before ordering.
What is the recommended replacement interval for these pulleys?
Idler pulleys do not have a strict replacement interval, but they should be inspected during every routine engine service (e.g., every 100-200 operating hours). Replace them if they are noisy, show signs of wobble, or the bearings feel rough when spun by hand.
What’s the difference between OEM and this aftermarket part?
This is an aftermarket replacement part, not an OEM component. It has been manufactured in an ISO 9002 certified facility and is built to meet or exceed original equipment specifications using comparable, high-quality materials. Each batch is inspected for quality and consistency.
How much is shipping and how fast is it?
We ship worldwide, with most standard deliveries arriving within 5–15 days. Standard shipping is free to most locations. If available for your region, expedited shipping options and their costs will be displayed at checkout.
What is the warranty and return policy?
This product is covered by a 1-year warranty against any manufacturing defects under normal marine use. Should an issue arise, please contact our support team with your order number. Returns of unused items in their original condition are accepted within our standard return window. Refer to our policy page or contact us for detailed instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything differs—even if your model is listed as compatible—do not order.
- This is an aftermarket replacement component, not an OEM part.
- Professional installation is recommended for safety and optimal performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — By working directly with our manufacturing partners, we provide fair pricing without compromising on materials or quality control.
Payment & Security
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