Mercury Quicksilver 865615Q10 Serpentine Belt — MerCruiser 5.7L & 6.2L MPI MIE
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Mercury Quicksilver 865615Q10 — Serpentine Accessory Drive Belt
| Part Number | 865615Q10 |
|---|---|
| Mercury Reference | 57-865615Q10 |
| SKU | 865615Q10 |
| Brand | Mercury / Quicksilver (OEM) |
| Product Type | Serpentine Accessory Drive Belt |
| System | MerCruiser MIE Accessory Drive |
| Belt Length | 2,195 mm |
| Idler Pulley Requirement | 4-1/4 in. diameter idler pulley |
| Cooling Configuration | Closed-cooled MIE applications |
| Supersedes | 865615010 / 57-865615010 / 86387610 / 57-86387610 |
| GTIN | 745061630505 |
| Weight | approx. 400 g |
Overview
Quicksilver 865615Q10 is a genuine Mercury Marine OEM serpentine accessory drive belt for selected MerCruiser MIE (marine inboard engine) applications with closed cooling and the 4-1/4 in. idler pulley configuration. It drives the alternator, coolant pump, power steering pump, and other accessories from the crankshaft pulley. On closed-cooled MIE installations, belt failure stops coolant circulation immediately — making proactive replacement at scheduled intervals essential.
Fitment note: Belt length on MerCruiser engines varies by accessory configuration, cooling system type, and idler pulley diameter. Confirm your engine model, serial number, cooling configuration, and idler pulley size (4-1/4 in.) before ordering. The part number printed on your existing belt is the fastest and most reliable fitment confirmation.
Supersession Chain
- Current part number: 865615Q10 / 57-865615Q10
- Supersedes: 865615010 / 57-865615010
- Supersedes: 86387610 / 57-86387610
- If your existing belt or service records show any of the superseded numbers above, 865615Q10 is the correct current OEM replacement.
Compatible Applications
- MerCruiser 350 MAG MPI MIE
- MerCruiser 350 MAG MPI Horizon MIE
- MerCruiser 5.7L MPI MIE
- MerCruiser 5.7L MPI Horizon MIE
- MerCruiser MX 6.2L MPI MIE
- MerCruiser MX 6.2L MPI Horizon MIE
- MerCruiser 6.2L MPI MIE
- MerCruiser 6.2L MPI Horizon MIE
- Configuration requirement: Closed-cooling system with 4-1/4 in. idler pulley — verify before ordering
- Always confirm using your engine serial number — similar MerCruiser engines with different accessory or cooling configurations use a different belt length
Service Interval
- Inspect the serpentine belt at every 100-hour service or annually, whichever comes first
- Replace immediately if cracking, fraying, glazing, missing ribs, or belt contamination (oil or coolant) is found
- Replace proactively at major service intervals — on a closed-cooled MIE, belt failure stops coolant circulation and causes rapid overheating
- Inspect the idler pulley, tensioner, and all accessory pulleys for wear, wobble, or bearing roughness each time the belt is replaced
- Confirm service intervals for your specific engine and serial range in the MerCruiser service manual
Installation Notes
- Before removing the old belt, photograph the routing or refer to the MerCruiser service diagram for your engine
- Inspect the 4-1/4 in. idler pulley, tensioner pulley, and all accessory pulleys for wear, wobble, and alignment while the belt is off
- Route the new belt exactly per the MerCruiser diagram — incorrect routing causes immediate belt failure or accessory damage
- Confirm the belt is fully seated in every pulley groove before starting the engine
- After startup, verify the belt tracks correctly on all pulleys with no edge riding, vibration, or noise
Technical FAQ
- What makes this belt different from other MerCruiser serpentine belts? Two specific details: the 2,195 mm belt length and the 4-1/4 in. idler pulley requirement. MerCruiser 5.7L and 6.2L engines can use different belt lengths depending on accessory and cooling configuration. Confirm both the idler pulley size and cooling system type, or cross-reference the part number printed on your existing belt.
- My belt shows 865615010 or 86387610 — is 865615Q10 the right replacement? Yes. Both 865615010 and 86387610 (and their 57- prefixed variants) are superseded by 865615Q10. This is the current OEM part for those applications.
- Should I replace the idler or tensioner at the same time? If either pulley shows wobble, bearing roughness, or the tensioner arm has lost spring tension, replacing them at the same time as the belt avoids a return service for a related failure. See related products below.
- My belt is squealing after installation — what should I check? Check belt tension first — a worn tensioner spring may not apply adequate load. Then inspect all pulleys for glazing, wobble, or misalignment. A new belt on a worn idler or misaligned pulley will squeal and wear rapidly.
- What happens if the belt breaks underway on a closed-cooled MIE? Belt failure stops the coolant pump and causes rapid engine overheating. Shut down immediately if belt failure is suspected. This is why proactive replacement at scheduled intervals is strongly recommended on MIE applications.
Parts Desk Insights
Best Use Case: This belt is best ordered as part of a scheduled 100-hour or annual service on closed-cooled MerCruiser MIE applications. Because the belt drives the coolant pump on these engines, running to failure is a genuine overheating risk — proactive replacement is the right call every time. It’s also the correct current replacement for any engine that previously used 865615010 or 86387610.
Common Issues: The most frequent ordering mistake is selecting this belt by engine displacement alone without confirming the cooling configuration and idler pulley size. MerCruiser 5.7L and 6.2L engines with open cooling or a different idler pulley diameter require a different belt. Always verify both details, or confirm by reading the part number off the existing belt, before ordering.
Related Products
- Mercury Quicksilver 865615Q06 Serpentine Belt — MerCruiser V8 5.0L–8.2L Sterndrive
- Mercury MerCruiser Serpentine Belt & Pulley Kit — 8M0150824
- Mercury MerCruiser Power Steering Pump Pulley — 8M0150723
- Mercury MerCruiser Seawater Pump Pulley — 8M0150724
- Sierra Serpentine Belt — Marine Inboard | 47-15103
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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