Serpentine Belt Idler Pulley – Fits MerCruiser V6 & V8 Engines (Replaces 865598, 818382, 8M6500024)
Serpentine Belt Idler Pulley – Fits MerCruiser V6 & V8 Engines (Replaces 865598, 818382, 8M6500024) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Serpentine Belt Idler Pulley – Fits MerCruiser V6 & V8 Engines ...
Product Details
This high-quality Serpentine Belt Idler Pulley is a direct-fit replacement for various MerCruiser V6 and V8 engines (model years 1996–2025) equipped with serpentine belt systems. It is also compatible with select General Motors Vortec V6 and Small Block V8 engines. Engineered for reliability, this pulley ensures proper belt tension and smooth engine operation.
It serves as a direct interchange for MerCruiser part numbers 865598, 818382, and 8M6500024, as well as JLM Marine 710-8M6500024.
- Engineered as a direct, bolt-on replacement for easy installation.
- Constructed from a durable, glass-fiber reinforced thermoplastic for longevity.
- Includes a pre-installed, sealed ABEC-3 ball bearing for optimal performance.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| MerCruiser | 865598 |
| MerCruiser | 818382 |
| MerCruiser | 8M6500024 |
| JLM Marine | 710-8M6500024 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This component is designed for the following MerCruiser engines equipped with a serpentine belt system.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| MerCruiser | 4.3L V6 (262 CID) | 190-220 | 4-Stroke | 1996–2025 | 865598/8M6500024 |
| MerCruiser | 5.0L V8 (305 CID) | 220-260 | 4-Stroke | 1996–2020 | 865598/8M6500024 |
| MerCruiser | 5.7L V8 (350 CID) | 250-350 | 4-Stroke | 1996–2025 | 865598/8M6500024 |
| MerCruiser | 5.8L V8 | 320-380 | 4-Stroke | 2000–2010 | 865598/8M6500024 |
| MerCruiser | 6.2L V8 (377 CID) | 300-350 | 4-Stroke | 2009–2025 | 865598/8M6500024 |
| MerCruiser | 8.1L V8 (496 CID) | 375-425 | 4-Stroke | 1996–2020 | 865598/8M6500024 |
Technical Specs
- Product Type
- Serpentine Belt Idler Pulley
- Installation
- Direct replacement
- Housing Material
- Thermoplastic resin composite (PA6/POM + 15-20% glass fiber)
- Housing Color
- Black
- Dimensions
- 76.2 mm outer diameter (3 inches), 15.875 mm inner diameter (5/8 inch), 25.4 mm width (1 inch), 31.75 mm total thickness (1.25 inches)
- Weight
- 0.104 kg (0.23 lb)
- Bearing Type
- Sealed deep groove ball bearing (ABEC-3)
- Max RPM
- 8000 RPM
- Radial Load Capacity
- 500 N
- Operating Temperature
- -30°C to +120°C
- Warranty
- 1-year against manufacturing defects
What’s in the Box
- 1 x Serpentine Belt Idler Pulley (Replaces 865598/818382/8M6500024)
Installation Notes
- Disconnect the negative battery terminal for safety.
- Locate the serpentine belt tensioner. Using an appropriate tool, release the tension and carefully slide the belt off the idler pulley.
- Unbolt and remove the old idler pulley from its mounting bracket. Note the orientation of any washers or spacers.
- Clean the mounting surface on the bracket to ensure the new pulley sits flush.
- Install the new idler pulley, making sure it is correctly aligned.
- Tighten the mounting bolt to the recommended torque specification of 15–25 Nm (11–18 ft-lb). Do not over-tighten.
- Reinstall the serpentine belt, confirming it is routed correctly around all pulleys according to your engine's diagram.
- Reconnect the battery, start the engine, and listen for any unusual noises while visually inspecting the new pulley for smooth operation.
Troubleshooting & FAQ
How do I know if this idler pulley fits my specific engine?
This pulley is designed for MerCruiser V6/V8 and some GM engines from 1996 onwards that use a serpentine belt system. The best way to confirm is to match the part number from your old pulley to one of the cross-reference numbers listed (865598, 818382, 8M6500024). Also, check your model against the compatibility table provided.
What are the signs of a failing idler pulley?
Common symptoms include a persistent high-pitched squeaking or grinding noise from the engine bay, visible wobble or play in the pulley while the engine is running, or accelerated or uneven wear on the edges of your serpentine belt.
When should I replace the idler pulley?
There is no strict replacement interval, but it is best practice to inspect the idler pulley whenever you replace your serpentine belt. If it feels rough when spun by hand, shows any side-to-side play, or appears cracked or worn, it should be replaced to prevent future belt failure.
Is this pulley plastic or metal?
The housing is made from a high-strength, glass-fiber reinforced thermoplastic resin composite. This material is an industry standard for modern pulleys, offering excellent durability and resistance to heat and wear, similar to the original OEM part.
Does this pulley come with the bearing pre-installed?
Yes, it is a complete assembly that includes a new, pre-installed sealed deep groove ball bearing (ABEC-3 rated) for a straightforward installation and reliable, long-lasting performance.
What is the correct installation torque for the mounting bolt?
The recommended installation torque is between 15–25 Nm. Applying the correct torque is critical; over-tightening can damage the bearing and lead to premature failure, while under-tightening can cause unsafe operation.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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