Volvo Penta Propeller Nut – 3851569

Volvo Penta Propeller Nut – Part Number 3851569

Brand: Volvo Penta (Genuine OEM)
Part Number: 3851569
Official Product Type: Propeller Nut
Supersedes: No superseded number identified in current references
Replaced By: No replacement listed — 3851569 is the current active part number

This is a genuine Volvo Penta OEM propeller nut for select Volvo Penta sterndrive and inboard propeller shaft assemblies. The propeller nut secures the propeller to the drive shaft and is a critical safety component — it must be in good condition and correctly torqued at all times. Replace during propeller service, propeller removal, or any time the nut is corroded, damaged, or shows signs of thread wear.

Specifications

• System: Propulsion / Drive Hardware
• Type: Propeller shaft retaining nut
• Exact thread specification and dimensions not published in current catalog. Confirm against your specific drive model, shaft configuration, and parts diagram before ordering.

Compatible Applications

Fitment must be confirmed by drive model, shaft configuration, and the correct Volvo Penta parts diagram before ordering:

• Select Volvo Penta sterndrive applications where the parts diagram specifies 3851569
• Select Volvo Penta inboard propeller shaft assemblies where specified

Serial Number Notice: Propeller nut thread size, diameter, and locking design vary by drive model and shaft configuration. Always verify 3851569 against your specific drive model, serial number, and parts diagram before ordering. Do not substitute by appearance alone.

Alternate & Cross-Reference Part Numbers

• 3851569 — Volvo Penta OEM (this part, active number)

Related Parts

• Volvo Penta Propeller Nut – 21631162 — Alternative propeller nut reference for other Volvo Penta applications
• Volvo Penta DuoProp Front Propeller Nut – 852196 — DuoProp-specific front propeller nut
• Volvo Penta Lock Washer – 853869 — Lock washer commonly used with propeller shaft hardware

When to Replace

Replace the propeller nut during any propeller removal or installation, or when the nut is corroded, thread-damaged, deformed, or no longer able to be correctly torqued. As a safety-critical fastener, the propeller nut should never be reused if there is any doubt about its condition.

Installation Notes

• Clean the propeller shaft threads before installing the new nut
• Inspect the shaft threads and propeller hub for damage before reassembly
• Torque to the Volvo Penta service manual specification for your specific drive model and shaft — do not estimate
• Install a new cotter pin or locking mechanism as required by the service manual — never reuse an old cotter pin
• Confirm the propeller is fully seated and the nut is correctly secured before returning the vessel to service

Service Interval

Inspect the propeller nut at every propeller removal and during annual drive service. Replace whenever the nut is removed and shows any corrosion, thread wear, or deformation, or as a matter of routine practice during propeller service. Refer to the Volvo Penta service manual for your specific drive model for torque specifications and locking hardware requirements.

Technical FAQ

Can I reuse the propeller nut after removing the propeller?
If the nut is in good condition with clean threads and no corrosion or deformation, it may be reused — but always inspect carefully before reinstalling. When in doubt, replace it. The propeller nut is a safety-critical component and the cost of a new nut is negligible compared to the risk of propeller loss.

Do I need a new cotter pin too?
Yes — always install a new cotter pin or locking device when reinstalling the propeller nut. Never reuse an old cotter pin. Check the Volvo Penta service manual for the correct locking hardware for your specific drive.

How do I know if this is the right nut for my drive?
Confirm by drive model, serial number, and the propeller shaft assembly section of the Volvo Penta parts diagram. Thread size and nut design vary across drive families — do not order by appearance or general drive family alone.

Parts Desk Insights

Propeller nuts are one of those parts that get overlooked until there’s a problem — and a loose or failed propeller nut is a serious safety issue on the water. We recommend replacing the nut any time the propeller comes off, especially on boats that see regular use or operate in saltwater where thread corrosion can develop quickly. If you’re doing propeller service, it’s also worth picking up a new cotter pin and inspecting the shaft threads and propeller hub at the same time. Have your drive model and serial number ready to confirm the correct nut before ordering — thread specifications vary more than most people expect across Volvo Penta drive families.