Mercury Quicksilver 865615Q10 Serpentine Belt – MerCruiser 5.7L & 6.2L MPI MIE
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Quicksilver 865615Q10 is a genuine Mercury Marine serpentine accessory drive belt measuring 2,195 mm in length, designed for selected MerCruiser MIE (marine inboard engine) applications with closed cooling and the 4-1/4 in. idler pulley configuration. It is the current replacement for the superseded belt numbers 865615010 and 86387610.
The serpentine belt drives the alternator, seawater or coolant pump, power steering pump, and other engine accessories from the crankshaft pulley. On closed-cooled MIE configurations, belt failure risks immediate loss of coolant circulation and engine overheating — making scheduled inspection and proactive replacement an important part of engine maintenance.
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 fitment confirmation.
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 — confirm before ordering
- Verify using your engine serial number — similar MerCruiser engines with different accessory or cooling configurations use a different belt length
Part Information
- Part number: 865615Q10
- Mercury reference: 57-865615Q10
- Brand: Mercury / Quicksilver
- Type: Serpentine accessory drive belt
- Length: 2,195 mm
- Idler pulley requirement: 4-1/4 in. diameter idler pulley
- Cooling system: Closed-cooled MIE applications
- Packaging: Genuine Quicksilver (OEM Mercury Marine)
- GTIN: 745061630505
- Condition: New / OEM
Supersession Chain
- Current number: 865615Q10 / 57-865615Q10
- Supersedes: 865615010
- Supersedes: 57-865615010
- Supersedes: 86387610
- Supersedes: 57-86387610
- If your existing belt or service records show any of the superseded numbers above, 865615Q10 is the correct current replacement
Service Interval
- Inspect the serpentine belt at every 100-hour service interval or annually, whichever comes first
- Replace immediately if cracking, fraying, glazing, missing ribs, or belt contamination (oil, coolant) is found
- Replace proactively at major service intervals — a belt failure underway on a closed-cooled MIE stops coolant circulation and causes rapid overheating
- Inspect idler pulley, tensioner, and all accessory pulleys for wear, wobble, or roughness each time the belt is replaced
- Confirm service intervals for your specific engine in the MerCruiser service manual for your model and serial range
Installation Notes
- Before removing the old belt, photograph or note the belt 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, bearing roughness, 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 running the engine
- After startup, verify the belt tracks correctly on all pulleys with no edge riding, vibration, or noise
Technical FAQ
Q: What’s the key fitment detail that distinguishes this belt from other MerCruiser serpentine belts?
Two things: 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 the accessory and cooling configuration — engines without closed cooling or with a different idler pulley diameter use a different belt. Confirm both the idler pulley size and cooling system type, or simply cross-reference the part number on your existing belt.
Q: My existing belt shows 865615010 or 86387610 — is 865615Q10 the correct replacement?
Yes. Both 865615010 and 86387610 (and their 57- prefixed variants) are superseded by 865615Q10. This is the current Mercury OEM part for those applications.
Q: 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, yes — replacing pulleys at the same time as the belt avoids a return service call for a related failure. See the Mercury MerCruiser Quicksilver Tensioner Pulley 865777 and the Mercury MerCruiser Serpentine Belt & Pulley Kit 8M0150824.
Q: 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.
Q: What happens if the belt breaks underway on a closed-cooled MIE?
On a closed-cooled inboard, belt failure stops the coolant pump and causes rapid engine overheating. Shut down immediately if belt failure is suspected and do not continue running. This is why proactive belt replacement at scheduled intervals is strongly recommended on MIE applications.
Related MerCruiser Belt & Pulley Products
- Mercury MerCruiser Quicksilver Serpentine Belt 865615010 — superseded OEM number, same application
- Mercury MerCruiser Quicksilver Tensioner Pulley 865777
- Mercury MerCruiser Serpentine Belt & Pulley Kit – 8M0150824
- Mercury MerCruiser Seawater Pump Pulley – 8M0150724
- Mercury MerCruiser Power Steering Pump Pulley – 8M0150723
- Mercury Idler Pulley Support Bushing 865193
- Mercury Serpentine Belt 8M0218433 – OEM Drive Belt
- Sierra Serpentine Belt – Marine Inboard | SKU 47-15103
Parts Desk Insights
The critical fitment detail for the 865615Q10 is not just the engine displacement — it’s the combination of the 2,195 mm belt length and the 4-1/4 in. idler pulley. MerCruiser 5.7L and 6.2L MPI MIE engines with different cooling or accessory configurations can use a different belt length, so displacement alone is not enough to confirm the right part. The safest check is the part number on the existing belt — if it shows 865615010, 86387610, or either of their 57- prefixed equivalents, the 865615Q10 is the correct current replacement. Best use case is a scheduled replacement during the 100-hour or annual engine service on closed-cooled MIE applications — given that the belt drives the coolant pump on these engines, running to failure is a real overheating risk. The most common issue we see is customers ordering a belt by engine displacement without confirming the cooling configuration or idler pulley size — always verify both before ordering on a closed-cooled MIE.
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
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
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All parts, components, hardware, manuals, and accessories must be included
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