Mercury MerCruiser Quicksilver O-Ring 25-54029 (2.800" × .103")
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Mercury Quicksilver O-Ring 25-54029 – 2.800” × .103”
This is a genuine OEM Mercury Marine / Quicksilver O-ring with a 2.800-inch inside diameter and a 0.103-inch cross-section. The larger diameter of this O-ring places it in housings, end caps, and fluid passage fittings found in MerCruiser sterndrive and engine assemblies — positions where a proper seal is critical to preventing coolant, oil, or fuel leaks. Always confirm the correct diagram position using your engine model and serial number before ordering.
Part Details
- Part Number: 25-54029 (also referenced as 54029)
- Brand: Mercury Marine / Quicksilver
- Official Product Type: O-Ring / Sealing Element
- Inside Diameter (ID): 2.800 inches
- Cross-Section (CS): 0.103 inches
- System: Varies by application — confirm via parts diagram
- Condition: New OEM
Compatible Applications
- MerCruiser sterndrive and inboard engine assemblies — specific position varies by model and serial number range
- Commonly found in housing end caps, fluid passage fittings, and larger-bore sealing positions
- Verify fitment using the Mercury parts diagram, engine model, and serial number before ordering
- The 2.800” ID distinguishes this from smaller-bore O-rings in the same assembly — do not substitute by size alone
Dimensions
- Inside Diameter: 2.800 in (71.12 mm)
- Cross-Section: 0.103 in (2.62 mm)
- Approximate weight: 10 g (0.01 kg)
Installation Notes
- Clean the O-ring groove and mating surfaces thoroughly before installation
- Lightly lubricate with the appropriate fluid or O-ring lubricant — do not use petroleum-based grease on fuel-system O-rings
- Seat evenly in the groove — do not twist or stretch during installation
- Replace all O-rings disturbed during disassembly; do not reuse compressed or hardened seals
- Follow the Mercury service manual for torque specifications on associated fasteners
Service Interval
Replace whenever the assembly is disassembled, when leakage is detected at the sealing surface, or when the O-ring shows visible compression set, cracking, or hardening. Mercury service procedures typically specify replacing all O-rings as a matter of course during overhaul.
Parts Desk Insights
Best use case: Resealing larger housing bores, end caps, and fluid passage fittings during overhaul or targeted leak repair. The 2.800” ID is a relatively large O-ring in the Mercury catalog, which helps narrow down the assembly location — if you’re working on a smaller fitting and this seems too large, double-check the diagram position number.
Common mistakes: Substituting by cross-section size alone without confirming the inside diameter — an O-ring that is too small in ID will be over-stretched and fail prematurely, while one that is too large will not seat properly. Also confirm the O-ring material is appropriate for the fluid being sealed: Mercury uses different compounds for fuel, coolant, and oil applications, and they are not interchangeable even when dimensions match.
Related Parts
- Mercury MerCruiser Quicksilver O-Ring 25-53421
- Mercury MerCruiser Quicksilver O-Ring 20826
- Mercury MerCruiser Quicksilver O-Ring 20863
- Mercury MerCruiser Quicksilver O-Ring 8M0204645
- Mercury MerCruiser Quicksilver O-Ring 23145
- Mercury MerCruiser Quicksilver Shift Pin O-Ring 25007
- Quicksilver O-Ring 26722
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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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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