Serpentine Belt Idler Pulley for Select MerCruiser 4.3L–8.1L Engines – Replaces 865598, 818382 & 8M6500024
Serpentine Belt Idler Pulley for Select MerCruiser 4.3L–8.1L Engines – Replaces 865598, 818382 & 8M6500024 is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
Serpentine Belt Idler Pulley for Select MerCruiser 4.3L–8.1L Engine...
Serpentine Belt Idler Pulley for Select MerCruiser 4.3L–8.1L Engines – Replaces 865598, 818382 & 8M6500024 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket serpentine belt idler pulley is designed for select MerCruiser stern-drive and inboard engines using a serpentine belt system. The listed engine families include select 4.3L, 5.0L, 5.7L, 6.2L and 8.1L MerCruiser applications.
Use the reference numbers below to compare this pulley with the component currently installed on your engine. Application coverage can vary by engine configuration, so confirm the original pulley and belt-system arrangement before ordering.
- Single replacement serpentine belt idler pulley.
- For select MerCruiser stern-drive and inboard engine applications.
- Fits applications using the corresponding serpentine belt pulley arrangement.
- Aftermarket replacement component; not manufactured by MerCruiser or Mercury.
Part Number Matrix
The following manufacturer reference numbers are associated with this replacement pulley.
| Brand | Reference Number |
|---|---|
| MerCruiser | 865598 |
| MerCruiser | 818382 |
| MerCruiser | 8M6500024 |
Engine & Model Compatibility
This pulley is listed for select MerCruiser stern-drive and inboard engines in the following displacement families. The engine must use the matching serpentine belt system and pulley arrangement.
| Brand | Engine Family | Application | Reference Numbers |
|---|---|---|---|
| MerCruiser | 4.3L V6 | Select stern-drive and inboard engines with the applicable serpentine belt system | 865598, 818382, 8M6500024 |
| MerCruiser | 5.0L V8 | Select stern-drive and inboard engines with the applicable serpentine belt system | 865598, 818382, 8M6500024 |
| MerCruiser | 5.7L V8 | Select stern-drive and inboard engines with the applicable serpentine belt system | 865598, 818382, 8M6500024 |
| MerCruiser | 6.2L V8 | Select stern-drive and inboard engines with the applicable serpentine belt system | 865598, 818382, 8M6500024 |
| MerCruiser | 8.1L V8 | Select stern-drive and inboard engines with the applicable serpentine belt system | 865598, 818382, 8M6500024 |
Important: The displacement list is not a confirmation for every year, serial number, horsepower rating or engine configuration. Match the reference number, pulley design and mounting arrangement before purchase.
Technical Specs
- Product Type
- Serpentine belt idler pulley
- Product Configuration
- Single replacement pulley
- Application
- Select MerCruiser stern-drive and inboard engines
- Listed Engine Families
- 4.3L, 5.0L, 5.7L, 6.2L and 8.1L
- Installation
- Replacement installation; use the engine manufacturer's service information for removal, alignment and fastener specifications
- Reference Numbers
- 865598, 818382 and 8M6500024
- UPC
- 745061648302
- Part Type
- Aftermarket replacement, not an OEM component
What’s in the Box
- 1 x Serpentine belt idler pulley
No belt, mounting hardware or additional pulley is included unless specifically shown or stated in the order details.
Installation Notes
- Disconnect the battery and allow the engine to cool before beginning work.
- Identify the serpentine belt routing and release belt tension using the correct tool for your engine.
- Remove the belt from the pulley and inspect the belt, adjacent pulleys and mounting hardware for wear or damage.
- Remove the existing pulley while noting the order and orientation of any spacers or washers.
- Clean the mounting surface and install the replacement pulley in the same orientation as the original.
- Tighten the mounting fastener to the specification provided in the engine or boat manufacturer's service information. Do not use a generic torque value in place of the applicable service specification.
- Route the serpentine belt according to the engine's belt-routing diagram and confirm that it is fully seated in every pulley.
- Reconnect the battery, start the engine and check for correct belt tracking, unusual noise or pulley wobble before returning the boat to service.
Troubleshooting & FAQ
How do I confirm that this pulley fits my engine?
First confirm that your engine is a MerCruiser stern-drive or inboard application in one of the listed 4.3L, 5.0L, 5.7L, 6.2L or 8.1L families. Then compare the pulley on your engine with the listed reference numbers—865598, 818382 or 8M6500024—and verify the mounting and belt arrangement. Displacement alone does not confirm fitment for every configuration.
Is this a complete pulley or a pulley set?
This listing is for one replacement serpentine belt idler pulley. It is not the two-pulley set associated with a separate combination listing.
What are common signs of a worn idler pulley?
Possible symptoms include belt squealing, grinding or chirping, visible pulley wobble, rough rotation, side-to-side play or abnormal belt wear. Inspect the belt system with the engine off and follow appropriate safety procedures.
Should I replace the belt at the same time?
Inspect the serpentine belt whenever the pulley is replaced. Replace the belt if it is cracked, glazed, frayed, contaminated or otherwise damaged, following the engine manufacturer's maintenance guidance.
Does this listing include installation hardware?
No additional hardware is specified as included. Reuse existing hardware only if it is serviceable and permitted by the applicable service instructions; otherwise obtain the correct replacement hardware separately.
Is this an OEM part?
No. This is an aftermarket replacement pulley associated with MerCruiser reference numbers 865598, 818382 and 8M6500024. MerCruiser and Mercury are referenced only for application and part-number identification.
What installation torque should I use?
Use the torque specification for your exact engine and pulley mounting arrangement from the applicable service manual. The correct value can vary by engine and hardware configuration.
Shipping speed & cost
We ship worldwide. Typical transit is 5–15 days, and standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
This product is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the standard return window when the item is unused and in its original condition. Contact support with your order details for assistance.
Safety & Important Info
- Confirm the reference number, pulley design, mounting arrangement and belt routing before ordering.
- Do not rely on engine displacement alone to confirm compatibility.
- Disconnect the battery and keep hands, clothing and tools away from moving components during testing.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended when the correct application or service specifications cannot be confirmed.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world applications.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing and practical replacement solutions for marine maintenance.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
