Quicksilver O-Ring 8M0204650 | Mercury MerCruiser OEM Seal
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Quicksilver OEM O-Ring — Part No. 8M0204650 / 25-8M0204650
- Part Number: 8M0204650
- Service Format: 25-8M0204650
- Supersedes: 29845 → 8M0204650 (current)
- Brand: Quicksilver (Genuine Mercury Marine OEM)
- Type: O-Ring — OEM sealing ring
- GTIN / UPC: 745061133709
- System: MerCruiser sterndrive — driveshaft housing, yoke, and related drive sealing applications
What This Part Does
This genuine OEM O-ring seals mating components in selected MerCruiser sterndrive and marine engine assemblies, preventing fluid and water intrusion at the joint. Mercury parts diagrams identify 8M0204650 as a yoke-end O-ring in Alpha One Gen II driveshaft-housing applications, with some assemblies specifying two O-rings at this location. It also appears in upper driveshaft, drive-gear, and coupler-end yoke assemblies across additional MerCruiser families.
Supersession note: 8M0204650 is the current active replacement for Mercury part 29845. If your parts diagram shows 29845, this is the correct OEM replacement. The service format 25-8M0204650 may appear in Mercury dealer ordering systems.
Critical matching note: MerCruiser sterndrive assemblies use many O-rings that look nearly identical. Match strictly by part number — do not select by appearance or approximate diameter alone.
Compatible Applications
- Alpha One Gen II sterndrive — driveshaft housing yoke-end O-ring (confirm quantity by diagram — some assemblies use two)
- Alpha One Gen II upper driveshaft and drive-gear assemblies
- Coupler-end yoke assemblies
- Selected Blackhawk sterndrive assemblies
- Any Mercury or MerCruiser assembly where the current diagram specifies 8M0204650, 25-8M0204650, or superseded number 29845
Confirm by exact engine or drive serial number and the current Mercury parts diagram before ordering.
Superseded Part Numbers
- 29845 → 8M0204650 (current active number)
- Service format: 25-8M0204650
When to Replace
- Any time the sealed joint is opened for service — O-rings are single-use
- O-ring is flattened, cut, cracked, hardened, or visibly deteriorated
- Fluid or water leak is present at the yoke, driveshaft housing, or associated joint
- Yoke, bearing, seal, or related drive component is being serviced
- Where the diagram specifies more than one 8M0204650, replace the full quantity for that assembly
Installation Notes
- Clean the O-ring groove and all mating surfaces — remove old lubricant, corrosion, and debris before installing the new seal
- Lubricate the O-ring only with the lubricant specified in the applicable Mercury service procedure
- Seat the O-ring evenly without twisting, stretching, or pinching
- Replace the full quantity specified in the diagram — do not reuse any O-rings that have been removed
- Inspect adjacent seals and hardware while the assembly is apart
Related Products
- Marine Gaskets, Seals & O-Rings
- Mercury MerCruiser Gaskets & Seals
- Mercury MerCruiser Engine Maintenance Parts
Parts Desk Insights
8M0204650 is one of those sterndrive O-rings where the part number matters far more than appearance — MerCruiser drive assemblies use several O-rings that look nearly identical, and selecting the wrong one will result in a premature seal failure that brings the drive back apart for repeat labor. The yoke-end location in particular is worth doing correctly the first time: it’s buried in the driveshaft housing, and getting back to it is not a quick job. Replace both O-rings where the diagram calls for two, and check the legacy number 29845 on older diagrams — 8M0204650 is the correct current part either way.
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.