Mercury MerCruiser Quicksilver Water Pump Base O-Ring 8M0204651
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Mercury MerCruiser Quicksilver Water Pump Base O-Ring – Part Number 8M0204651
- Part Number: 8M0204651
- Brand: Mercury Marine / Quicksilver
- Type: Water Pump Base O-Ring — OEM Replacement Seal
- Supersedes: Mercury 30224 (8M0204651 is the current replacement for 30224)
- Replaced By: No current superseding number identified — 8M0204651 is active in Mercury parts references.
- System: Cooling System — Lower Unit Water Pump Assembly
- Diagram Position: Seats at the water pump base, sealing the base against the gear housing; typically 1 required per applicable assembly.
- Dimensions (30224 specification): Approximately 1.859 in. (47.2 mm) ID × 0.139 in. (3.5 mm) cross-section
What This Part Does
The water pump base O-ring seals the pump base against the gear housing, preventing cooling water leakage around the base and maintaining proper sealing within the lower-unit water pump assembly. It is a one-time-use seal — a fresh O-ring should be installed any time the pump base is disturbed.
Compatible Applications
- Selected Mercury outboard gearcases, including applications using water pump base assembly 812966A7
- Selected Mercury outboard gearcases — 45 Jet and 50 HP (earlier 30224 applications; verify against current diagram)
- Selected MerCruiser sterndrive gearcase and water pump configurations
Mercury uses several similar-looking O-rings throughout water pump and gearcase assemblies. Confirm fit using your engine or drive serial number and the factory parts diagram before ordering.
When to Replace
- Any time the water pump base is removed
- Existing O-ring is flattened, cracked, hardened, or cut
- Leakage visible around the pump base
- Lower unit being resealed or rebuilt
- Water pump service exposes the original O-ring
- Corrosion or debris has compromised the sealing surface
Installation Notes
- Clean the pump base groove and all mating surfaces before installation
- Remove old lubricant, corrosion, and debris that could interfere with sealing
- Lubricate the replacement O-ring only as specified in the applicable Mercury service procedure
- Install without twisting or pinching the seal
- Do not reuse the original O-ring after the pump base has been disturbed
Alternate & Superseded Part Numbers
- Mercury / Quicksilver 8M0204651 (current)
- Mercury 30224 (superseded by 8M0204651)
Related Parts
- Mercury Water Pump Base to Face Plate Gasket 27-39625
- Mercury Quicksilver 192043 Water Pump Base Gasket — 6–15 HP Outboard
- Mercury Quicksilver 19202001 Water Pump Plate Gasket — 6 / 8 / 9.9 HP Outboard
- Mercury Outboard Water Pump Impeller 8-Blade 8M0135803
- Mercury Outboard Water Pump Gasket — Gear Housing 16160004
- Shop All Marine Gaskets, Seals & O-Rings
Parts Desk Insights
The water pump base location is what makes this O-ring easy to mix up — Mercury uses several seals in the lower unit that are nearly identical in appearance but differ in compound and size. Always match by part number (8M0204651 or the older 30224) and confirm against your gearcase diagram rather than sizing by eye. This is a low-cost seal that is worth including any time you have the water pump apart; replacing it on reassembly is inexpensive insurance against reopening the lower unit for a preventable leak.
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.