Mercury Quicksilver 865615Q06 Serpentine Belt – MerCruiser V8 5.0L–8.2L Sterndrive
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Quicksilver 865615Q06 is a genuine Mercury Marine serpentine accessory drive belt measuring 2,667 mm in length, designed for compatible MerCruiser V8 sterndrive and inboard engines with closed cooling and power steering. It is the current Quicksilver replacement for the superseded OEM numbers 865615006, 8638766, and 8610491, and is cross-referenced by the Sierra aftermarket equivalent 18-15102.
The serpentine belt drives the alternator, circulating water pump, power steering pump, and other engine accessories from the crankshaft pulley. A failed belt on a closed-cooled MerCruiser stops coolant circulation immediately — creating an overheating risk that makes proactive scheduled replacement the right approach rather than waiting for a failure.
⚠️ Fitment note: Multiple belt variants exist within the MerCruiser 865615 family. The Q06 (2,667 mm) is specifically used with closed cooling and power steering on applicable V8 configurations — similar engines without closed cooling or power steering, or with a different accessory arrangement, may use a different belt. Confirm using your engine serial number and the part number printed on your existing belt before ordering.
Compatible Applications
- MerCruiser 5.0L V8 sterndrive — closed-cooling applications (confirm serial range)
- MerCruiser 5.7L / 350 MAG V8 sterndrive — closed-cooling applications (confirm serial range)
- MerCruiser 350 MAG MPI Alpha/Bravo — closed cooling with power steering (confirm serial range)
- MerCruiser 5.0L MPI Alpha/Bravo — closed cooling with power steering (confirm serial range)
- MerCruiser 377 MAG MPI Alpha/Bravo — closed cooling with power steering (confirm serial range)
- MerCruiser MX 6.2L MPI Alpha/Bravo — closed cooling (confirm serial range)
- MerCruiser 6.2L V8 sterndrive — selected closed-cooling configurations
- MerCruiser 7.4L V8 sterndrive — selected configurations (confirm serial range)
- MerCruiser 8.1L V8 sterndrive/inboard — selected configurations (confirm serial range)
- MerCruiser 8.2L V8 — selected configurations (confirm serial range)
- Configuration requirement: Closed-cooling system with power steering — engines without this arrangement may use a different belt length
- Confirm fitment using engine serial number and the part number on your existing belt
Part Information
- Part number: 865615Q06
- OEM number: 865615006
- Mercury reference: 57-865615Q06
- Brand: Mercury / Quicksilver
- Type: Serpentine accessory drive belt
- Length: 2,667 mm
- Application: MerCruiser V8 sterndrive and inboard engines, closed cooling with power steering
- Packaging: Genuine Quicksilver (OEM Mercury Marine)
- GTIN: 745061630468
- Condition: New / OEM
Supersession & Cross-Reference Numbers
- Current: 865615Q06 / 57-865615Q06
- Supersedes: 865615006 / 57-865615006
- Supersedes: 8638766 / 57-8638766
- Supersedes: 8610491 / 57-8610491
- Sierra aftermarket equivalent: 18-15102
- GTIN: 745061630468
- If your existing belt or service records show any superseded number above, 865615Q06 is the current correct replacement
865615 Belt Family — Variant Reference
- 865615Q06 / 865615006 — 2,667 mm — this listing; V8 closed-cool with power steering
- 865615Q03 — different length/configuration; verify before substituting
- 865615Q10 — 2,195 mm; MerCruiser 5.7L & 6.2L MPI MIE closed-cool with 4-1/4" idler — verify before substituting
Service Interval
- Inspect at every 100-hour service interval or annually, whichever comes first
- Replace immediately at any sign of cracking, fraying, glazing, missing ribs, or belt contamination (oil or coolant)
- Proactive replacement at scheduled intervals is strongly recommended — belt failure on a closed-cooled engine stops coolant circulation immediately
- Inspect idler pulleys, tensioner pulley, alternator pulley, and circulating pump pulley for wear, wobble, and alignment at every belt replacement
- Confirm the exact service interval for your engine in the Mercury/MerCruiser service manual for your model and serial range
Installation Notes
- Before removing the old belt, photograph the routing or refer to the MerCruiser service diagram for your engine model
- While the belt is removed, inspect the tensioner, idler pulleys, alternator pulley, circulating pump pulley, and power steering pump pulley for wear, wobble, bearing roughness, and alignment
- Route the new belt exactly per the MerCruiser diagram — incorrect routing causes immediate belt failure or accessory damage
- Confirm every rib is fully seated in the corresponding pulley groove before running the engine
- After startup, verify the belt tracks correctly on all pulleys with no edge riding, vibration, or squealing
Technical FAQ
Q: What is the key fitment detail that distinguishes 865615Q06 from other 865615-series belts?
The belt length: 2,667 mm. This is longer than the Q10 variant (2,195 mm) and is specifically used on V8 MerCruiser sterndrive engines with closed cooling and power steering. Confirm the length and configuration match by checking the part number on your existing belt or looking up your engine serial number in the Mercury parts catalog.
Q: My existing belt shows 865615006, 8638766, or 8610491 — is 865615Q06 the correct replacement?
Yes. All three numbers are superseded by 865615Q06, which is the current Mercury OEM replacement for those applications.
Q: Can I use the Sierra 18-15102 instead?
The Sierra 18-15102 is the aftermarket equivalent cross-reference for this belt. If you prefer an OEM Quicksilver part, 865615Q06 is the correct choice. Both reference the same application.
Q: Should I replace the tensioner or idler pulleys at the same time?
If any pulley shows wobble, bearing roughness, or the tensioner arm has lost spring tension, yes — replacing them with the belt in the same service visit avoids a return job for a related failure. See the Mercury MerCruiser Quicksilver Tensioner Pulley 865777 and the complete Serpentine Belt & Pulley Kit 8M0150824.
Q: My belt squeals 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 MerCruiser, belt failure immediately stops the circulating water pump and causes rapid engine overheating. Shut down as quickly as safely possible. Do not continue running with a failed serpentine belt on a closed-cooled engine.
Related MerCruiser Belt & Drive Products
- Mercury MerCruiser Quicksilver Serpentine Belt 865615Q03 — related variant; verify before substituting
- Mercury Quicksilver 865615Q10 Serpentine Belt – MerCruiser 5.7L & 6.2L MPI MIE — related variant (2,195 mm); verify before substituting
- 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 key to getting the right belt in the 865615 family is the 2,667 mm length combined with the closed-cooling and power steering configuration — that combination is what the Q06 is built for. Best use case is a scheduled replacement on any of the listed V8 MerCruiser sterndrive configurations during the 100-hour or annual engine service. The most common issue is customers ordering a belt by engine displacement alone without confirming the cooling system type or belt number — a 5.7L without closed cooling may use a different belt entirely, so always verify the existing belt number or engine serial number first. If your records show 865615006, 8638766, or 8610491, the Q06 is the correct current replacement — no further cross-referencing needed. As with all MerCruiser serpentine belts, proactive replacement is strongly recommended over waiting for a failure: a broken belt underway on a closed-cooled engine stops coolant circulation immediately and can cause serious overheating damage in a very short time.
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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