Sierra Gimbal Bearing 18-21006 | MerCruiser Bravo & Gen II Sterndrive
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Sierra Gimbal Bearing 18-21006 — MerCruiser Bravo & Gen II Sterndrive
Part Number: 18-21006 (Sierra) | Brand: Sierra | OEM Cross-Reference: MerCruiser 21006
The Sierra 18-21006 is a direct-replacement gimbal bearing engineered to OEM fit and dimensional specifications for MerCruiser Bravo One, Bravo Two, Bravo Three, and Gen II sterndrive applications. The gimbal bearing supports the driveshaft at the transom plate and allows the sterndrive unit to pivot smoothly through its full range of steering and trim movement. A worn or failed gimbal bearing causes grinding noise at the transom, rough steering, and — if ignored — accelerated wear to the bellows assembly, driveshaft, and u-joints.
Weight: 533 g | Quantity: 1 bearing per package
Compatible Applications
- MerCruiser Bravo One sterndrive (OEM gimbal bearing ref 21006)
- MerCruiser Bravo Two sterndrive (OEM gimbal bearing ref 21006)
- MerCruiser Bravo Three sterndrive (OEM gimbal bearing ref 21006)
- MerCruiser Gen II sterndrive applications specifying gimbal bearing 21006
Fitment Notice: The Bravo/Gen II gimbal bearing (18-21006) and the Alpha One gimbal bearing are not interchangeable. Confirm your drive generation and existing OEM bearing number before ordering. For Alpha One and earlier applications, see Gimbal Bearing 47-21001.
Specifications
- Manufacturer Part Number: 18-21006
- Brand: Sierra
- Product Type: Gimbal Bearing — complete replacement unit
- System: Sterndrive transom / gimbal housing assembly
- Weight: 533 g
- OEM Cross-Reference: MerCruiser 21006
Service Interval
Inspect the gimbal bearing any time the sterndrive is removed. Replace when any of the following are observed:
- Grinding, rumbling, or clicking noise at the transom during operation or steering
- Rough, binding, or notchy sterndrive pivot movement
- Visible pitting, corrosion, or roughness on the bearing surfaces
- During bellows replacement service — labor overlap makes simultaneous bearing replacement cost-effective
- After any significant impact to the drive or transom assembly
Installation Notes
- Remove the sterndrive unit and transom assembly to access the gimbal ring
- Inspect the gimbal housing bore, bellows, inner and outer u-joints, and driveshaft seal surfaces during the same service
- Press the new bearing into the gimbal ring to the correct depth — use the manufacturer-specified bearing installation driver to avoid damage to the bearing race
- Replace the bellows set and all seals as a complete assembly when performing gimbal bearing service
- Grease bearing contact surfaces and pivot pins per the engine manufacturer's service manual specification before reassembly
- Torque all fasteners to specification
Cross-Reference Part Numbers
- Sierra: 18-21006
- MerCruiser OEM: 21006
- Distributor/Catalog SKU: 47-21006
Related Products
- Gimbal Bearing 47-21001 — Alpha One / Volvo Penta Applications
- MerCruiser Gimbal Bearing Kit 879194A01 — Alpha One
- MerCruiser Gimbal Bearing Kit 879194A02 — Alpha One
- MerCruiser Gimbal Housing Bushing Kit 805041A2
- MerCruiser Gimbal Housing Lock Nut 11-34087
- MerCruiser Bellows Assembly 8M0062406
- MerCruiser Bellows Assembly 8M0124227
- Sierra Transom Seal Kit 47-8205
- Sierra Transom Seal Kit 47-82061
- MerCruiser Lower Unit Seal Kit 26-33144A2
Parts Desk Insights
Best use case: The 18-21006 is the right bearing for any Bravo or Gen II sterndrive transom service. If you're already pulling the drive for bellows replacement, always inspect — and in most cases replace — the gimbal bearing at the same time. The labor to access it is identical, and a failed bearing discovered later means a full repeat teardown.
Common issue: The most frequent ordering error is confusing Bravo and Alpha generation bearings. Customers often search by engine rather than drive model — the gimbal bearing is specific to the sterndrive unit generation, not the engine. If your boat has a MerCruiser engine but an Alpha One drive, you need 47-21001, not this bearing. Always confirm the drive model plate on the transom assembly before ordering.
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
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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.
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