Mercury Quicksilver Screw 5/16"-24 × 1.12" 20639
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Mercury Quicksilver Screw 5/16"-24 × 1.12" — Part 20639
A genuine Quicksilver OEM screw for Mercury and MerCruiser assemblies, catalogued as 10-20639. Thread size is 5/16"-24 (UNF fine thread) × 1.12" length. This part has been discontinued and is no longer available through current Mercury production channels. No old-stock inventory is available — if you need this screw, a cross-reference to a standard 5/16"-24 UNF × 1-1/8" grade fastener with the correct finish and head style may be the only path forward.
Key Features
- Genuine Quicksilver OEM fastener — original factory specification
- Part number: 20639 / 10-20639
- Thread: 5/16"-24 UNF (fine thread) × 1.12" length
- Discontinued — no longer in current Mercury production
Fitment & Application
Use this screw where the Mercury or MerCruiser parts diagram specifies part number 20639 or 10-20639. Fitment varies by engine model, drive type, and serial number range — always confirm against your specific parts diagram before ordering or substituting.
When to Replace
Replace when the screw is corroded, stripped, rounded, stretched, or has been removed from a critical assembly during service and cannot be safely reused. Fine-thread fasteners in particular should not be reused if there is any sign of thread damage or galling.
Installation Notes
Confirm thread pitch (fine thread, 24 TPI), length, diameter, and finish against the diagram position before installation or substitution. Follow the Mercury service manual for torque specifications and locking compound requirements. If substituting with a standard fastener, match head style, drive type, and surface finish to the original.
Related Products
- Mercury Quicksilver Screw 5/16"-18 × 3/4" — 25299 — Coarse-thread 5/16"-18 UNC variant, limited old-stock available
- Mercury MerCruiser Screw .250-20 × .625 — 14070 — 1/4"-20 UNC screw for Mercury / MerCruiser assemblies
- Mercury MerCruiser Quicksilver Stainless Screw 28635 — Stainless OEM screw for corrosion-critical positions
- Mercury MerCruiser Transom Plate Mounting Screw 8M0215010 — OEM transom plate mounting screw
Parts Desk Insights
Best use case: This listing is most useful as a reference when you need to identify the original OEM specification for the 10-20639 position in a Mercury or MerCruiser parts diagram. Since the part is fully discontinued with no available stock, the practical next step is a cross-reference: a standard 5/16"-24 UNF × 1-1/8" cap screw or machine screw in the correct head style and finish will typically be the substitute. Confirm head style, drive type, and any coating or plating requirements from the service manual before substituting in a structural or sealing-critical position.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
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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.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
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