Volvo Penta Lock Nut – 990990

The Volvo Penta 990990 is a genuine Volvo Penta OEM lock nut used as diagram-specific structural hardware on select Volvo Penta diesel engine, sterndrive, and transom shield assemblies. This locking fastener is used where the Volvo Penta parts diagram calls for 990990, helping secure components exposed to vibration, clamp load, and marine operating stress in engine, drive, and shield hardware locations.

Key Features

• Genuine Volvo Penta factory OEM lock nut.
• Volvo Penta part number: 990990.
• Structural locking fastener for select Volvo Penta marine engine, drive, and transom shield assemblies.
• Listed weight: 0.03 lb.
• Used in vibration-sensitive mounting and fastening locations where a locking nut is specified.
• Commonly associated with select D6 diesel, DPH-E, DPI-A, and transom shield hardware diagrams.
• Replaces older Volvo Penta part reference 971084 where confirmed by serial number and diagram.

Application Compatibility

Common where-used application groups include select Volvo Penta assemblies by model, serial number, and diagram location, including:

• D6-300I-G applications where specified
• D6-340I-G applications where specified
• D6-380I-G applications where specified
• D6-440I-G applications where specified
• D6-440I-WJ-G applications where specified
• D6-480I-G applications where specified
• DPH-E sterndrive applications where specified
• DPI-A sterndrive applications where specified
• TSK DPH-E transom shield assemblies where specified
• TSK DPI-A transom shield assemblies where specified

Use this lock nut only where the Volvo Penta parts diagram specifically calls for 990990.

Fitment Notice

Confirm fitment by Volvo Penta engine serial number, drive model, transom shield assembly, fastener location, and exact parts diagram before ordering. Volvo Penta uses similar lock nuts and structural fasteners across multiple D6, drive, bracket, and shield assemblies, so thread size or appearance alone is not enough to confirm fitment.

When This Part Needs Replacement

Replace this lock nut if the original fastener is missing, corroded, rounded, cross-threaded, stretched, damaged, or no longer holds its locking tension. It should also be replaced whenever the Volvo Penta service procedure requires new locking hardware after disassembly, especially in high-vibration engine, drive, and transom shield locations.

Installation Notes

Install this nut only in the exact diagram location that calls for 990990. Inspect the matching stud or bolt, washer stack, bracket, shield surface, drive mounting hardware, and surrounding components before reassembly. Do not substitute a standard non-locking nut in structural or vibration-sensitive locations. Follow the Volvo Penta service manual for the correct torque value, thread condition, washer placement, and any required locking procedure for the specific assembly.

Alternate/Superseded Part Numbers

• 990990 Volvo Penta lock nut
• 971084 older Volvo Penta reference; verify by serial number and diagram before substitution

Parts Desk Insight

Lock nuts used on Volvo Penta drive and transom shield assemblies are small but important service parts. Once the locking feature has been used, worn, or damaged during removal, replacing the nut helps maintain proper clamp security in a vibration-heavy marine environment. Matching the fastener by Volvo Penta part number and diagram location helps keep the hardware stack correct.

Shipping: Ships same or next day for fast Canada wide shipping.