Mercury MerCruiser Quicksilver Serpentine Belt 865615010 | 2195 mm | 5.0L–6.2L V8

Mercury MerCruiser Quicksilver Serpentine Belt 865615010

• Part Number: 865615010 (Mercury service format: 57-865615010)
• Brand: Mercury Marine / MerCruiser / Quicksilver
• Official Product Type: Multi-Rib Serpentine Accessory Drive Belt
• Belt Length: Approximately 2195 mm
• Belt Type: Multi-rib serpentine
• System: Engine accessory drive (alternator, seawater pump)
• Cross-Reference Numbers: 865615Q10, 57-865615010, 57-86387610
• Replaced By: No confirmed further supersession — 865615010 is current

What This Belt Does

The Mercury Marine 865615010 is a genuine OEM multi-rib serpentine belt for selected MerCruiser small-block V8 engines. It transfers power from the crankshaft to the alternator and seawater pump in the engine’s accessory drive system. Many documented applications are MIE inboard engines with closed cooling systems using a 4-1/4 inch idler pulley configuration. The multi-rib design provides strong, quiet pulley grip under the high-load conditions of marine accessory systems.

Compatible Applications

• MerCruiser 5.0L V8 (305 CID) — 2001 and later MIE inboard configurations
• MerCruiser 5.7L V8 (350 MAG / 350 MAG MPI) — MIE inboard configurations
• MerCruiser 6.2L MPI — MIE inboard configurations
• MerCruiser MX 6.2L MPI Horizon

Confirm by engine model, serial number, cooling system configuration (open or closed), and accessory-drive pulley arrangement before ordering. Engines of the same displacement can use different belt lengths depending on the alternator, seawater pump pulley diameter, and idler pulley size.

Cross-Reference Numbers

• Mercury / Quicksilver: 865615010, 57-865615010, 865615Q10
• Earlier Mercury reference: 57-86387610

Note: 865615Q10 and 865615010 are related Mercury part numbers for this belt family. Confirm which number your engine’s parts diagram specifies before ordering — see also the Mercury Quicksilver 865615Q10 Serpentine Belt listing for the Q10 application.

Service Interval

Inspect the serpentine belt annually at seasonal service. Replace immediately if the belt shows cracking, glazing, fraying, rib separation, or excessive stretch. A slipping or squealing belt under load, or one riding low in the pulley grooves, should be replaced regardless of age. A failed serpentine belt simultaneously disables the alternator and seawater pump, causing loss of battery charging and raw water cooling flow.

When to Replace

• Belt is visibly cracked, glazed, frayed, or has separated ribs
• Belt squeals or slips under accessory load
• Belt rides low or unevenly in the pulley grooves
• Alternator or seawater pump output is inconsistent
• Belt has been in service beyond the manufacturer’s recommended interval
• Idler pulley or tensioner replacement requires belt removal

Installation Notes

• Inspect all pulleys (alternator, seawater pump, idler) for wear, groove damage, and alignment before installing
• Check the idler pulley bushing for wear — a worn bushing causes belt misalignment and premature failure
• Do not force the belt over pulley flanges — route by hand using the idler to release tension
• Set belt tension per Mercury service specifications — both over- and under-tensioning cause premature failure
• Rotate the engine by hand to confirm correct seating across all pulley ribs
• Recheck tension after the first operating period

Technical FAQ

What is the difference between 865615010 and 865615Q10?
These are related Mercury part numbers in the same belt family. Both are documented for MerCruiser 5.7L and 6.2L MPI MIE applications. Confirm which number appears in your engine’s parts diagram by serial number — they are not always interchangeable without diagram confirmation.

Why does this belt fit some 5.7L engines but not others?
MerCruiser 5.7L engines were produced in multiple configurations with different accessory layouts, cooling systems (open vs. closed), and pulley sizes. The 865615010 is specifically documented for MIE closed-cooling applications with a 4-1/4 inch idler pulley. Always verify by serial number.

What else should I inspect when replacing this belt?
Inspect the idler pulley and bushing, seawater pump pulley, and alternator pulley for wear or damage. A worn idler bushing (865193) is a common cause of belt misalignment and accelerated wear on this accessory drive system.

Can I use an aftermarket belt?
Sierra 18-15122 is documented as an aftermarket equivalent. For critical marine applications, using a genuine Mercury Marine OEM belt eliminates fitment uncertainty from aftermarket dimensional tolerances.

Related Parts

• Mercury Quicksilver 865615Q10 Serpentine Belt — MerCruiser 5.7L & 6.2L MPI MIE
• Mercury Quicksilver 865615Q06 Serpentine Belt — MerCruiser V8 5.0L–8.2L Sterndrive
• Mercury MerCruiser Serpentine Belt & Pulley Kit 8M0150824
• Mercury Idler Pulley Support Bushing 865193
• Mercury MerCruiser Seawater Pump Pulley 8M0150724
• Mercury MerCruiser Power Steering Pump Pulley 8M0150723
• Quicksilver 70 Amp Alternator Delco Serpentine 862031T1

Parts Desk Insights

The most common issue with 865615010 orders is customers selecting by displacement alone without confirming the cooling system configuration and idler pulley size. This belt is specifically documented for MIE closed-cooling applications with a 4-1/4 inch idler pulley — the same engine in an open-cooling or sterndrive configuration may use a different belt entirely. Always verify by engine serial number and parts diagram. When replacing this belt, check the idler pulley bushing (865193) at the same time: a worn bushing is a frequent cause of belt noise, misalignment, and early failure on this accessory drive, and it is inexpensive to replace alongside the belt.