Mercury MerCruiser Quicksilver O-Ring 25-31986
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You have 30 days to request a return. All sale items are final sale.
OEM O-Ring for Mercury & MerCruiser Assemblies
This genuine Quicksilver O-Ring is a broad-use sealing ring found across a wide range of Mercury outboard and MerCruiser sterndrive assemblies. At 2.635 in. (67 mm) I.D. × 0.210 in. (5.3 mm) width, it’s a precision-fit seal designed to hold up in the demanding conditions of a marine environment. When an O-ring fails, even a small leak can lead to bigger problems — this is the correct OEM replacement to restore a proper, pressure-tight seal.
Key Details
- OEM Part Number: 25-31986
- Base Reference: 31986
- Type: O-Ring
- Dimensions: 2.635 in. / 67 mm I.D. × 0.210 in. / 5.3 mm width
- GTIN / UPC: 745061135390
- Genuine OEM — not aftermarket
Common Applications
This O-ring appears across many Mercury and Mariner outboard families including select 35, 40, 45, 50, 60, 65, and 70 HP models, as well as older MerCruiser sterndrive applications including “0” sterndrive (1965–1966) and 60 Renault 68 I/L4 (1965–1968). Always verify compatibility using your engine’s model number, serial number, and the exact Mercury parts diagram before ordering — this part appears across many different assemblies and locations.
Cross-Reference Part Numbers
- Mercury / Quicksilver: 25-31986, 31986
- Sierra: 18-7160
- GLM: 83340
- Mallory: 9-76545
- Volvo Penta: 3852866 (related cross-reference)
- OMC / Johnson / Evinrude: 0508490, 0913850, 3852866 (related cross-reference)
When to Replace
Replace this O-ring whenever the related assembly is opened, or if the original seal is flattened, brittle, swollen, cracked, or no longer sealing properly. Reusing a compressed or damaged O-ring risks repeat leaks.
Installation Tips
Clean the O-ring groove and mating surface before installation. Lightly lubricate with the service-manual-approved lubricant where specified, and ensure the O-ring seats evenly without twisting, stretching, or rolling during assembly.
Related Hardware
Parts Desk Insights
Best use case: Direct OEM replacement when the Mercury parts diagram calls for 25-31986 at a specific assembly location. Because this is a broad-use O-ring that appears across many engine families and locations, the safest match is the exact diagram callout — not horsepower alone. The physical dimensions (67 mm I.D.) can help confirm the part, but serial number and diagram location are the most reliable way to avoid ordering the wrong seal. Cross-reference numbers like Sierra 18-7160 and GLM 83340 are widely stocked alternatives if the OEM part is unavailable.
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.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.