Sierra Gimbal Bearing 18-2100 | MerCruiser / OMC / Volvo Penta
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Sierra Gimbal Bearing 18-2100
Part Number: 18-2100 (Sierra) Ā |Ā UPC: 030-999-310262
The Sierra 18-2100 is a heavy-duty, greaseable Link-Belt gimbal bearing designed for the transom assemblies of MerCruiser, OMC Cobra / King Cobra, and Volvo Penta sterndrive systems. It supports and aligns the engine-to-sterndrive input shaft as it passes through the transom housing, while allowing controlled angular movement of the drive.
Bearing Specifications
- Construction: Link-Belt
- Service type: Greaseable
- Outside diameter: 3.46 in. / 88 mm
- Inside diameter: 1.38 in. / 35 mm
- Width: 1.30 in. / 33 mm
Dimensions are reference fitment values based on the OEM cross-reference bearing family.
Compatible Applications
MerCruiser
- 120 / 140 HP Ā (Serial: 2791957ā6225576)
- 165 HP Ā (Serial: 2763442 and up)
- 225-S Ā (Serial: 3856268ā4200499)
- 228 HP Ā (Serial: 4782330 and up)
- 233 HP Ā (Serial: 4200500 and up)
- 250 HP Ā (Serial: 4791300 and up)
- R / MR
- Alpha One
- Alpha One Gen II
- Bravo One
- Bravo Two
- Bravo Three
- Blackhawk
OMC
- OMC Cobra
- OMC King Cobra
- Selected 1980sā1990s Cobra-family sterndrive applications
Volvo Penta
- DP-S / DP-S1
- SX-C
- Selected SX-M transom shield / drive configurations
- Associated 3.0 L, 4.3 L, 5.0 L, 5.7 L, 5.8 L, 7.4 L, and 8.2 L engine applications
Fitment Notice
This bearing spans several generations of MerCruiser, OMC, and Volvo Penta drives. Not every transom assembly uses the same bearing. Before ordering, confirm:
- Drive model and generation
- Engine or drive serial number
- Existing OEM bearing number
- Transom assembly type
- Bearing bore dimensions
OEM & Cross-Reference Part Numbers
Mercury / MerCruiser
- 30-60794A2
- 30-60794A4 ā superseded by 30-879194A02
- 30-60794B4
- 30-879194A02
See also: Mercury MerCruiser Gimbal Bearing Kit 879194A01 | Mercury MerCruiser Gimbal Bearing Kit 879194A02
OMC
- 983937
- 3853807
Volvo Penta
- 3853807
- 21752712
Other Aftermarket
- GLM 21900
- Mallory 9-72410
When to Replace the Gimbal Bearing
- Growling or rumbling noise from the transom area, especially when turning under power
- Bearing feels rough or catches when rotated by hand
- Excessive radial play in the input shaft
- Visible corrosion, water intrusion, or grease contamination
- Engine-to-drive alignment cannot be maintained due to bearing wear
Installation Notes
Gimbal bearing replacement requires sterndrive removal. During service:
- Inspect bellows for cracking or water intrusion ā see U-Joint Bellows and MerCruiser Bellows Assembly 8M0062406
- Inspect input shaft and U-joints
- Check bearing bore and retaining components
- Install bearing squarely into the transom housing
- Align grease passage correctly on greaseable installations
- Lubricate with specified marine grease
- Verify engine alignment with the correct alignment tool before reinstalling the drive
Incorrect engine alignment after installation accelerates wear on both the gimbal bearing and drive coupler.
Related Parts
- Sierra 18-21006 Gimbal Bearing ā MerCruiser Bravo & Gen II Sterndrive
- Mercury MerCruiser Gimbal Bearing Kit 879194A01 | Alpha One
- Mercury MerCruiser Gimbal Bearing Kit 879194A02 | Alpha One
- Sierra Transom Seal Kit ā 47-8205
- Sierra Transom Seal Kit ā 47-27721
- Sierra Transom Seal Kit ā 47-82061
- OMC Bellows Kit
- Volvo Drive Bellows Kit
- OMC Sterndrive/Cobra Exhaust Bellows
- Volvo Penta Bellows Kit 876294
- Mercury Quicksilver Gimbal Housing Lock Nut 11-34087
- Quicksilver 94996Q2 Bell Housing Gasket Kit ā MerCruiser R, MR & Alpha One Gen II
- Sierra Cobra Outdrive Mounting Gasket Set (47-2613)
Parts Desk Insights
The Sierra 18-2100 covers one of the most common transom bearing interchange families across three major sterndrive brands. Customers most often need this bearing after noticing a growling or grinding noise from the back of the boat at low RPM or during tight turns ā classic gimbal bearing wear symptoms that worsen over time if ignored.
The most reliable way to confirm this is the right bearing: check whether the existing bearing or OEM number cross-references to MerCruiser 30-879194A02, OMC 3853807, or Volvo Penta 21752712. If it does, 18-2100 is in the correct interchange family. Always double-check the transom assembly and drive serial before finalizing the order, particularly on Volvo Penta SX-M configurations, which can use different bearings depending on the transom shield version.
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 ā 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 ā 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.