Mercury MerCruiser Quicksilver O-Ring 201951 | 0.487 x 0.103 in.
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Mercury / MerCruiser Quicksilver O-Ring 201951
Part Number: 201951 | Service Format: 25-201951 | Size: 0.487 in. ID × 0.103 in. cross-section | Supersedes: 20195 | GTIN: 745061129689
Genuine Mercury / MerCruiser OEM O-ring used across multiple Mercury and MerCruiser sealing applications. On MerCruiser Alpha One Gen II and Bravo gear-lube monitor systems, 201951 is the O-ring used on the 90-degree gear-lube fitting assembly, with two O-rings required per applicable fitting assembly. Mercury’s current OEM number is 201951 (service format 25-201951), replacing the earlier 20195. Because 201951 is a shared O-ring appearing in several Mercury assemblies, always confirm the diagram position and required quantity for your specific application.
Specifications
- Brand: Mercury / MerCruiser / Quicksilver
- Part Number: 201951
- Service Format: 25-201951
- Type: OEM O-ring
- Inside Diameter: 0.487 in. (12.37 mm)
- Cross-Section: 0.103 in. (2.62 mm)
- GTIN / UPC: 745061129689
- Weight: ~0.02 kg per unit
- Supersedes: 20195 (25-20195)
- Additional Cross-Reference: F40342
- Current OEM Number: 201951 (25-201951)
Compatible Applications
Fitment and required quantity must be confirmed against the Mercury parts diagram for your specific engine model and serial number. 201951 is a shared O-ring — its location and quantity vary by assembly.
- MerCruiser Alpha One Gen II — gear-lube monitor 90° fitting assembly (qty 2 per fitting)
- MerCruiser Bravo — gear-lube monitor 90° fitting assembly (qty 2 per fitting)
- Mercury outboard idle-relief tube assemblies (selected applications)
- Mercury 90 HP / 95XR Jet Drive (selected applications)
- Mercury jet-pump nozzle / rudder assemblies (selected applications)
- Selected Mercury cooling-system fitting assemblies
Diagram Position & Assembly Context
For MerCruiser Alpha One Gen II and Bravo gear-lube monitor systems, Mercury parts diagrams show:
- 861150T02 — 90° fitting assembly
- 201951 — O-ring, 0.487 × 0.103 in. — quantity 2
- 627021 — smaller O-ring, 0.301 × 0.070 in. — quantity 1 (separate — do not confuse with 201951)
- 861163 — 90° quick connector
Do not substitute the smaller 627021 O-ring for 201951 — they appear in the same fitting assembly but are different sizes and positions.
When to Replace
- The fitting or sealed component is being disassembled for service
- Gear-lube or water leakage is present at the fitting
- The O-ring is flattened, permanently compressed, cut, swollen, hardened, or cracked
- The service procedure specifies replacement during reassembly — best practice is to replace any O-ring that has been disturbed
Installation Notes
- Clean the O-ring groove and mating surface thoroughly before installing the new O-ring
- Lubricate with the sealant or lubricant specified for the exact Mercury assembly — do not use petroleum-based grease on EPDM or other elastomers unless confirmed compatible
- Avoid twisting or pinching the O-ring during installation
- On Alpha One Gen II and Bravo gear-lube monitor fittings: verify both 201951 O-rings are correctly seated before reconnecting the fitting assembly
Related Parts & Service Items
- Mercury MerCruiser Trim Cylinder O-Ring Kit 87400A2
- Mercury Quicksilver Lower Unit Seal Kit 26-33144A2 — Alpha One Gen 1
- Mercury Upper Gearcase Seal Kit 26-32511A1
- Mercury MerCruiser Gearcase Drain & Fill Screw Seal 8M0187157
- Mercury MerCruiser Gear Housing Oil Passage Seal 455771
- Quicksilver 94996Q2 Bell Housing Gasket Kit — Alpha One Gen II
Parts Desk Insights
Best use case: 201951 is the O-ring to reach for during any Alpha One Gen II or Bravo gear-lube monitor service where the 90-degree fitting is being disconnected. Since two are required per fitting, it’s worth confirming the quantity before ordering — replacing both at the same time is the right call, as a used O-ring alongside a new one is a common source of a slow weep that shows up shortly after service.
Common customer issue: Confusing 201951 with the smaller 627021 O-ring that appears in the same fitting assembly. They look similar but are different sizes and seat in different positions. The diagram clearly calls out both by number and quantity — if you’re unsure which one you need, our parts desk can walk you through the diagram for your specific drive before you order.
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.
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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For return authorization, please contact our support team before shipping anything back.