Mercury MerCruiser - Pinion Nut - 11-35921
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The Mercury MerCruiser Quicksilver Pinion Nut 11-35921 is an OEM lower-unit gearcase fastener used to secure the pinion gear to the driveshaft in compatible Mercury outboard and MerCruiser drive assemblies. This nut helps maintain proper gear positioning and preload inside the gear housing under high torque and load.
Key Features
- Genuine Mercury/Quicksilver pinion nut
- Part number: 11-35921
- Also referenced as 35921
- Thread size: 5/8"-18 UNF fine thread
- Listed thread dimension: .625-18
- Requires 1-1/16" wrench
- Secures pinion gear to driveshaft
- Critical lower-unit gearcase fastener
Engine & Drive Compatibility
Used across select Mercury outboards, Mercury Jet applications, and MerCruiser sterndrive gear housings. Commonly associated with mid-to-high horsepower Mercury 2-stroke outboards, including 40 HP through 300 HP applications, select 45/50/60/100/115 HP configurations, V6 Black Max, XR2, XR4, XR6, Pro Max models, and Mercury 45 Jet, 55 Jet, 105 Jet, and 110 Jet assemblies.
Serial Number Fitment Notice
Verify fitment by engine or drive serial number, gearcase diagram, driveshaft configuration, and pinion gear assembly before ordering. Pinion hardware can vary by gearcase family, shaft size, gear ratio, and production range.
When This Part Needs Replacement
Replace this pinion nut during lower-unit rebuilds, driveshaft removal, pinion gear service, gearset replacement, or anytime the original nut has been removed, damaged, rounded, corroded, or compromised.
Installation Notes
Pinion nut service requires proper lower-unit disassembly tools and Mercury service procedures. Do not reuse a worn or previously stressed locking nut in critical gearcase service. Confirm gear preload, backlash, shim setup, and contact pattern during reassembly.
Alternate/Superseded Part Numbers
Primary Mercury references: 11-35921 and 35921. Common aftermarket interchanges include Sierra Marine 18-3718, Sierra Marine 18-3719, GLM Products 11190, and Recmar REC11-35921.
Parts Desk Insight
The pinion nut is buried inside the gearcase, but it is not a throwaway detail. Replacing it during gearcase service helps protect the gearset from movement, preload issues, and expensive repeat teardown.
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.