Mercury Quicksilver Water Pump Base O-Ring 26722 | 25-26722
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Mercury Quicksilver Water Pump Base O-Ring — Part No. 26722 / 25-26722
- Part Number: 26722
- Service Number: 25-26722
- Brand: Quicksilver (Genuine Mercury Marine OEM)
- Type: O-Ring — Water Pump Base / Driveshaft Carrier Seal
- GTIN: 745061132344
- Supersedes: 20266 → 26722
- Typical Quantity: 1
- System: Cooling / Water Pump / Gearcase Lower Unit
What This Part Does
This genuine OEM O-ring seals the water pump base and driveshaft carrier area on Mercury outboard gearcases. Depending on the assembly and diagram, it may be called an O-ring, water pump base or O-ring, driveshaft carrier — both refer to this same part number in the relevant exploded views. A failed seal in this location allows water ingestion or coolant loss, making this a critical service component during any lower-unit or water-pump rebuild.
Compatible Applications
Confirm by serial number and current Mercury parts diagram before ordering. Documented applications include:
- Mark 35A
- Mark 50 / 50E
- Mark 55 / 55E
- Mark 75-series
- 300 / 350
- 400 / 450
- 500 / 50
- 600
- 40 / 402
- 70 HP 3-cylinder
- Selected 15, 20, and 25 HP outboards (later Mercury listings)
Serial Number & Diagram Requirements
Because 26722 is used across multiple Mercury gearcase generations, always confirm the exact engine serial number and cross-reference the water-pump or gearcase diagram for your specific model before ordering. The part's position may be labeled differently depending on the assembly revision.
When to Replace
- Any time the water pump base or driveshaft carrier is removed
- When the existing O-ring is flattened, cracked, hardened, or cut
- If water intrusion or cooling loss is found near the water-pump base
- During lower-unit rebuilds — treat as a one-time-use seal
Installation Notes
- Inspect the mating groove and sealing surfaces for nicks or corrosion before fitting
- Install without twisting, pinching, or rolling the O-ring
- Lightly lubricate with a compatible marine grease before seating
- Follow the Mercury service manual for torque and reassembly sequence
Diagram Position & Related Assembly Parts
In Mercury water-pump diagrams, 26722 is located at the water pump base. Associated parts in the same assembly area include:
- 77177A1 — Water Pump Base Assembly
- 90562 — Water Pump Base Seal
- 79831 — Water Pump Base Seal
- 19552 / 19553 — Water Pump Base Gaskets
- 32768 — Face Plate
- 89983T — Water Pump Impeller (Mercury MerCruiser Quicksilver)
Related Products
Parts Desk Insights
Best used as the OEM seal during any Mercury outboard water pump service or lower-unit rebuild where the diagram specifies 26722. This is one of the more frequently overlooked seals in a water pump kit — customers who skip it on a pump rebuild often return with a cooling complaint within a season. Always match by part number: O-rings that appear identical can differ in compound hardness and will fail prematurely in the wrong application. If your engine has been repowered or updated, cross-reference the current Mercury diagram to confirm 26722 hasn't been further superseded for your serial range.
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.