Mercury Quicksilver Hex Head Cap Screw 10-34353 | 3/8"-16 x 1" OEM MerCruiser Fastener — Pack of 5

Mercury Quicksilver Hex Head Cap Screw 10-34353 — Pack of 5

Part Number: 10-34353 (short ref: 34353)
Brand: Mercury / Quicksilver
Product Type: Hex Head Cap Screw (OEM)
Thread Size: 3/8"-16 UNC coarse thread
Length: 1.00" (under head)
Head Style: Hex head
System: Engine hardware — bracket, pump, pulley, and accessory drive mounting
Supersedes: F1867, F2202 (earlier factory references — verify by diagram)
Sold As: Pack of 5
Approximate Weight: 15 g per screw / ~75 g per pack

What This Part Is

The Mercury Quicksilver 10-34353 is a genuine OEM hex head cap screw called out across a wide range of MerCruiser engine, bracket, pump, pulley, and accessory mounting locations. At 3/8"-16 coarse thread and 1.00" in length, it is a precision-grade fastener specified for locations where a generic hardware-store substitute is not appropriate. Sold here as a pack of 5 — useful when the diagram calls for multiple at the same assembly location.

Compatible Applications

Always confirm fitment by engine serial number and diagram position before ordering. This screw appears across many diagram locations — the diagram is the definitive reference for the correct length and grade at each specific position.

• MerCruiser MCM 120 / 140 / 2.5L / 3.0L inline-4 — bracket and accessory mounting locations per diagram
• MerCruiser 4.3L / 4.3LX / 4.3LH V6 — bracket and pump mounting locations per diagram
• MerCruiser 5.0L / 5.7L / 350 MAG / 350 MAG MPI small-block V8 — accessory and pulley mounting per diagram
• MerCruiser 330 HP / 340 MIE / 370 TRS / 400 TRS / 454 MAG MPI big-block — where diagram specifies
• MerCruiser D7.3L D-Tronic 300 diesel — where diagram specifies
• Alpha and Bravo engine package accessory mounting locations — where diagram specifies

Diagram Positions

• Seawater pump mounting — see Mercury MerCruiser Seawater Pump Kit 8M0139995
• Seawater pump pulley mounting — see Mercury MerCruiser Seawater Pump Pulley 8M0150724
• Serpentine belt and pulley assemblies — see Mercury MerCruiser Serpentine Belt & Pulley Kit 8M0150824
• Alternator, power steering pump, and accessory drive bracket mounting
• Engine-mounted sensor and accessory brackets

Dimensions

• Thread: 3/8"-16 UNC coarse thread
• Length: 1.00" (under head)
• Head Style: Hex head cap screw
• Wrench Size: 9/16" hex

When to Replace

• Original screw is missing, seized, or corroded
• Threads are stripped, cross-threaded, or the screw no longer clamps securely
• Head is rounded or damaged and cannot be properly torqued
• Incorrect hardware was previously installed at this location
• Any time the assembly is disassembled and the screw shows wear or corrosion

Installation Notes

• Verify mounting hole threads are clean and undamaged before installation
• Compare the removed fastener to the replacement for thread pitch, length, and head style before installing
• Torque to the specification in the Mercury service manual for the exact assembly location — torque varies by location
• Do not substitute a longer screw in blind holes — it can bottom out before the component is properly clamped
• Apply thread-locking compound only where specified by the Mercury service manual for this location

Part Number Cross-Reference

• Current OEM: 10-34353
• Short Reference: 34353
• Supersedes: F1867, F2202

Technical FAQ

Q: Can I use a standard hardware-store 3/8"-16 x 1" bolt instead?
A: Not recommended for OEM-specified locations. Mercury OEM fasteners are made to specific strength grades, coatings, and dimensional tolerances for marine engine environments. A generic bolt may look identical but differ in ways that matter for long-term reliability.

Q: What is the difference between 10-34353 and other 3/8"-16 MerCruiser screws?
A: Length, coating, and strength grade. MerCruiser uses multiple 3/8"-16 screws in different lengths (3/4", 1", 1-1/4", etc.) across the same engine. Always match by part number and diagram position, not just thread size.

Q: What do the superseded numbers F1867 and F2202 mean?
A: These are earlier Mercury factory reference numbers for the same fastener. If your older parts list shows either number, 10-34353 is the current OEM replacement. Verify against the current diagram for your engine serial number.

Q: How many screws does my engine need?
A: Quantity varies by engine model and the number of locations where this screw appears in the diagram. Check the parts diagram for your specific engine serial number before ordering. This pack of 5 covers most common multi-fastener assembly locations.

Parts Desk Insights

Best use case: The pack of 5 is the right choice when you have a Mercury parts diagram calling for 10-34353 at multiple locations in the same assembly — most commonly seawater pump service, pulley assembly work, and accessory bracket replacement on small-block and big-block MerCruiser engines.

Common issues: The most frequent mistake is ordering by thread size alone. MerCruiser uses similar 3/8"-16 screws in multiple lengths across the same engine — always match by part number and diagram position. A second common issue is underordering — check the diagram for your engine before ordering to confirm the full quantity needed at each location.

Related Parts

• Mercury Quicksilver Hex Head Cap Screw 10-34353 | 3/8"-16 x 1" OEM MerCruiser Engine Fastener (single)
• Mercury MerCruiser Seawater Pump Kit 8M0139995
• Mercury MerCruiser Seawater Pump Pulley 8M0150724
• Mercury MerCruiser Serpentine Belt & Pulley Kit 8M0150824
• Mercury MerCruiser Power Steering Pump Pulley 8M0150723
• MerCruiser Nut OEM 24652 — Pack of 5