Mercury Propeller Shaft Nut 858869 – 7/8"-14 UNF OEM
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Mercury Propeller Shaft Nut 858869 – 7/8"-14 UNF
Part Number: 858869 (Mercury catalog prefix: 11-858869)
Brand: Mercury Marine (Quicksilver OEM)
Official Product Type: Propeller Shaft Nut
Thread Specification: 7/8"-14 UNF (0.875"-14)
System: Propeller / Lower Unit Hardware
Condition: New OEM
What It Does
The Mercury 858869 is a genuine OEM propeller shaft nut with a 7/8"-14 UNF thread specification. This nut secures the propeller to the propeller shaft on selected Mercury outboard and MerCruiser sterndrive applications. Using the correct OEM nut ensures proper thread engagement, correct torque retention, and compatibility with the tab washer or cotter pin retention system used on your specific drive.
Compatible Applications
- Selected Mercury outboard engines with 7/8"-14 UNF propeller shaft threads — verify by model and serial number
- Selected MerCruiser sterndrive applications — verify by model and serial number
Serial Number Note: Propeller shaft hardware varies by engine model, shaft diameter, and production serial range. Always confirm this part number against the Mercury Parts Catalog using your exact engine model and serial number before ordering. Do not order by thread spec alone — nut style, depth, and retention method also vary.
Dimensions
Thread: 7/8"-14 UNF (fine thread, 0.875" nominal diameter, 14 threads per inch)
Supersedes / Alternate Part Numbers
- 858869 — current Mercury OEM part number
- 11-858869 — alternate catalog prefix format, same part
Kit Contents
Single OEM propeller shaft nut. Tab washers, cotter pins, and thrust hubs are sold separately — see related products below.
Service Interval
Inspect the propeller nut every time the propeller is removed. Replace if the nut is corroded, the threads are damaged, or the nut has been rounded from improper tool use. Mercury service manuals specify a torque value and retention method (tab washer or cotter pin) for each application — always follow the manual for your specific engine.
Technical FAQ
Q: Can I reuse the propeller nut after removing the propeller?
In many cases yes, if the nut is in good condition and threads are clean and undamaged. However, if the nut shows any corrosion, thread damage, or deformation, replace it. Some Mercury applications use a prevailing-torque (self-locking) nut that should be replaced after removal.
Q: What torque should I use?
Torque specifications vary by engine model and shaft size. Always refer to the Mercury service manual for your specific engine. Do not guess — under-torquing can allow the propeller to loosen under load; over-torquing can damage the shaft threads.
Q: Do I need a tab washer or cotter pin with this nut?
Depends on your application. Many Mercury propeller installations use a tab washer or cotter pin as a secondary retention device. Check your parts diagram and service manual to confirm what retention hardware is required for your specific engine.
Related Products
- Mercury Propeller Nut Kit 8M0056235
- Mercury MerCruiser Quicksilver Propeller Nut Kit 69578Q1
- Mercury Quicksilver Propeller Nut Kit 11-52707Q1
- Mercury MerCruiser Propeller Tab Washer 14-34817
- Mercury MerCruiser Propeller Shaft Toothed Lockwasher 13-423511
- Mercury MerCruiser Quicksilver Keyed Washer 14-18323
Parts Desk Insights
Best Use Case: This is the right part when you need an exact OEM replacement nut for a propeller removal and reinstall — particularly when the original nut is corroded from saltwater exposure or has been rounded by an improper tool. It’s also the correct choice when a service manual or warranty requirement specifies OEM hardware. Keep a spare on hand if you regularly pull the prop for inspection or cleaning.
Common Mistakes: The most common error is assuming any 7/8"-14 nut will work. Nut depth, style (flanged vs. plain), and retention method vary across Mercury applications — a nut that fits the threads but is the wrong style may not retain the propeller correctly or may interfere with the thrust hub. Always match by part number from the diagram, not by thread spec alone. Another frequent mistake is skipping the tab washer or cotter pin — the nut alone is not always sufficient retention on all applications.
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.