Mercury Quicksilver Gimbal Housing Lock Nut 11-34087 | 1/2"-13 Nyloc for MerCruiser Transom Assembly

Gimbal Housing Lock Nut for MerCruiser Transom Assemblies

The Mercury Quicksilver 11-34087 is an OEM 1/2"-13 red Nyloc hex locking nut used to secure the gimbal housing mounting hardware on select MerCruiser sterndrive transom assemblies. The red nylon locking insert maintains clamping force between the outer transom assembly and the inner transom plate, resisting vibration-induced loosening in a high-load, high-vibration mounting environment.

Nyloc nuts should be replaced any time they are removed from a critical mounting location. Once the nylon insert has been compressed and torqued, it loses a portion of its locking effectiveness — reusing a previously torqued Nyloc nut in a gimbal housing application is not recommended.

Part Information

• Part Number: 11-34087
• Short Reference: 34087
• Brand: Mercury / Quicksilver
• Official Product Type: Gimbal Housing Lock Nut
• Barcode / UPC: 745061136991
• Thread Size: 1/2"-13 UNC (coarse thread)
• Locking Type: Red nylon insert (Nyloc)
• Approximate Weight: 0.02 kg (0.04 lb)

Compatible Applications

• MerCruiser R sterndrive transom assembly
• MerCruiser MR sterndrive transom assembly
• MerCruiser Alpha One Generation 1 transom assembly
• MerCruiser Bravo I transom assembly
• MerCruiser Bravo II transom assembly
• MerCruiser Bravo III transom assembly
• Select legacy MerCruiser inline and V8 sterndrive packages where this nut is shown in the gimbal housing or transom assembly diagram

Fitment Note: Verify by drive or transom serial number, gimbal housing diagram, and original hardware stack-up before ordering. Transom hardware can vary by drive generation, housing style, bolt length, and production range.

System & Diagram Position

This nut is part of the transom assembly / gimbal housing mounting system. In the Mercury parts diagram it appears in the transom assembly section, at the gimbal housing mounting bolt locations where it secures the housing to the transom plate. It is typically used with a corresponding bolt and washer stack — confirm the full hardware stack-up in the diagram for your specific drive serial number before ordering.

Dimensions

• Thread: 1/2"-13 UNC coarse thread
• Locking Insert: Red nylon (Nyloc)
• Hex Size: Standard 1/2"-13 hex (3/4" wrench)

When to Replace

• Any time the nut is removed from the gimbal housing mounting location
• Nylon insert is visibly worn, melted, loose, or no longer grips the bolt threads
• Nut is corroded, rounded, or otherwise damaged
• During any gimbal housing removal, transom reseal, or bellows replacement service

Service Interval

Gimbal housing lock nuts do not have a standalone replacement interval, but should be replaced any time the transom assembly is disassembled. They are a standard replacement item during bellows service, transom reseal, and gimbal housing removal.

Installation Notes

• Install in the correct gimbal housing mounting locations shown in the Mercury parts diagram for your drive
• Inspect the mounting bolts, washers, and transom plate for corrosion or damage before reassembly
• Do not reuse previously torqued Nyloc nuts — the locking insert loses effectiveness after the first torque cycle
• Follow the Mercury service manual torque specification and tightening sequence for the gimbal housing mounting hardware
• Confirm the full hardware stack (bolt, washer, nut) matches the diagram before final assembly

Related Parts

• Mercury MerCruiser Quicksilver Gimbal Housing Washer 21900
• Mercury MerCruiser Gimbal Housing Bushing Kit 805041A2
• Mercury MerCruiser Bellows Assembly 8M0062406
• Mercury MerCruiser Bellows Assembly 8M0124227
• Mercury MerCruiser Bellows Assembly 36222A2
• Sierra Transom Seal Kit 47-82061
• Sierra Transom Seal Kit 47-8205
• Mercury MerCruiser Quicksilver Mount Kit 8M0103028
• Mercury Cotter Pin 18-54929

Technical FAQ

Q: Can I reuse this lock nut after removing the gimbal housing?
A: No. Nyloc nuts are designed for single use in critical fastener applications. Once the nylon insert has been compressed and torqued, it does not return to its original locking geometry. Always replace with a new nut during reassembly.

Q: What torque specification applies to this nut?
A: Torque specifications vary by drive model and production range. Refer to the Mercury service manual for your specific sterndrive for the correct gimbal housing mounting torque and tightening sequence.

Q: How many of these nuts does my transom assembly require?
A: The quantity varies by drive model and transom configuration. Check the Mercury parts diagram for your specific drive serial number to confirm the number of nuts in the gimbal housing mounting hardware stack.

Q: Is this the same nut used on both Alpha One and Bravo drives?
A: This part number appears across multiple MerCruiser drive generations including Alpha One Gen 1 and Bravo I/II/III, but always verify against the parts diagram for your specific drive serial number before ordering.

Parts Desk Insights

Best use case: This nut is the right call during any gimbal housing removal — bellows replacement, transom reseal, or gimbal bearing service. It is inexpensive enough that it should always be replaced rather than reused, and having a few on hand before starting a transom job avoids a parts run mid-service.

Common mistakes: The most frequent mistake is reusing the old Nyloc nut after reassembly. A previously torqued Nyloc nut looks fine but no longer provides the same locking resistance — in a high-vibration gimbal housing location, that matters. A second common mistake is ordering only one when the transom assembly requires multiple — check the diagram for your drive before ordering to confirm the full quantity needed.