Mercury MerCruiser Seal 8M0058391
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Mercury MerCruiser Seal – 8M0058391
Ensure a proper seal when servicing your sterndrive or outboard gearcase with the Mercury MerCruiser Seal 8M0058391. This genuine Mercury / Quicksilver OEM gearcase drain screw seal (washer) is used with the gear lube drain and fill screws to create a watertight seal and prevent water intrusion into the gearcase.
The seal is made from rubber-coated stainless steel, providing a durable sealing surface that helps maintain proper gear oil containment and prevents leaks during operation.
Key Features
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Genuine Mercury Marine / Quicksilver OEM gearcase seal
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Rubber-coated stainless steel washer design
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Provides a watertight seal for gearcase drain/fill screws
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Helps prevent water intrusion into the gearcase
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Durable construction designed for marine environments
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Recommended replacement when performing gear lube changes
Part Details
OEM Part Number: 8M0058391
Mercury Reference Number: 26-8M0058391
Product Type: Gearcase drain screw seal / washer
Material: Rubber-coated stainless steel
Application: Gearcase drain and fill screw sealing washer
Typical Packaging: Often sold in packs of 2
Compatible Mercury & MerCruiser Engines
Used on gearcase drain and fill screws with 3/8-16 threads, including:
Mercury Outboards
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Mercury 2.5HP – 400HP outboards
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Mercury Two-Stroke outboards
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Mercury FourStroke outboards
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Mercury Pro XS outboards
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Mercury Verado outboards
MerCruiser Sterndrives
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Alpha One
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Alpha One Gen II
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Bravo One
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Bravo Two
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Bravo Three
This seal is compatible with most Mercury and Mariner outboards and all MerCruiser sterndrives using 3/8-16 gearcase drain/fill screws.
Function
The drain screw seal is installed under the gearcase drain or fill screw to prevent leaks and stop water from entering the gearcase.
Replacing the seal during gear lube service helps:
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Prevent gear oil leaks
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Stop water intrusion into the gearcase
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Maintain proper lubrication of internal gears
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Protect the sterndrive or gearcase from internal damage
Even a small leak can allow water to mix with gear oil, which can cause gearcase corrosion or gear failure.
Important Compatibility Note
Gearcase drain screw seals should always be replaced during gear lube changes to maintain a proper seal. Always verify the gearcase drain screw size (3/8-16) and engine or drive serial number before ordering to ensure correct fit.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
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.