Mercury MerCruiser Quicksilver Washer 12-8M0207778 (.344 x .625 x .063)
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
Genuine Mercury OEM Washer — .344" x .625" x .063"
This is the genuine OEM flat washer used in Mercury MerCruiser and Quicksilver assemblies wherever a .344" ID × .625" OD × .063" thick washer is specified in the parts diagram. Manufactured to factory tolerances, it ensures correct clamping load and sealing surface protection during reassembly.
Key Specifications
- Part Number: 12-8M0207778
- Dimensions: .344" ID × .625" OD × .063" thick
- Genuine OEM — not aftermarket
- Compatible with Mercury, MerCruiser, and Quicksilver assemblies calling for this part number
Fitment
Match this washer to your Mercury parts diagram using your engine model, serial number, and assembly location. Similar washers across Mercury product lines can vary by thickness and diameter — always confirm the part number before ordering.
When to Replace
Replace any time the washer is removed during service, shows signs of deformation, corrosion, or scoring, or whenever the fastener it seats is being replaced.
Installation
Ensure mating surfaces are clean and free of debris. Follow the Mercury service manual for correct orientation, torque specifications, and any locking compound requirements.
Parts Desk Insights
Best use case: This washer is most commonly needed during thermostat housing, water pump, and manifold fastener service on MerCruiser inboard and stern drive engines. It provides the correct load-spreading surface under bolts and screws in areas where a standard hardware-store washer would not meet factory tolerances. Always order by the diagram part number — dimensions alone are not sufficient to confirm fitment across all Mercury assemblies.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 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.