Volvo Penta Gearlube Stern Drive O-Rings Duo 3852045 3855081 SX-M, SX-A, DPS-A

Replacing the Volvo Penta Genuine Factory OEM Gearlube Stern Drive O-Rings (part numbers 3852045 and 3855081) for the stern drive lower unit is a straightforward maintenance task to prevent gear lube leaks and ensure proper sealing of the dipstick, vent, and drain plugs. These O-rings are compatible with Volvo Penta models such as SX-M, SX-A, DPS-A, and DPS-M drives. Below is a step-by-step guide based on general marine maintenance practices and information from sources like eBay and Amazon. Always consult your Volvo Penta service manual for model-specific instructions and safety precautions.

Tools and Parts Needed

• Parts:
  • Volvo Penta OEM O-Rings: Dipstick O-ring (3852045), Vent/Drain O-ring (3855081, typically two required). Available as a duo set on eBay or Amazon.
  • Volvo Penta gear lube (or compatible marine gear oil, e.g., Quicksilver 80w-90).
• Tools:
  • Flathead screwdriver or appropriate socket (for drain/vent plugs, often 3/8″ or 10mm).
  • Gear lube pump (e.g., Slippery Pete Lower Unit Gear Oil Pump).
  • Drain pan
  • Clean rags and degreaser (for cleaning surfaces).
  • Torque wrench (if specified in the manual for plug tightening).
  • Gloves and safety glasses.
• Optional:
  • Marine grease (e.g., Quicksilver 2-4-C with Teflon) for O-ring lubrication.

Step-by-Step Process

1. Preparation:
   • Position the Boat: Ensure the boat is on a trailer or in a dry dock with the stern drive accessible. Engage the boat’s safety mechanisms (e.g., kill switch, battery disconnected).
   • Gather Materials: Verify you have the correct OEM O-rings (3852045 for dipstick, 3855081 for vent and drain).
   • Set Up Drain Pan: Place a drain pan under the lower unit to catch gear lube.
2. Drain the Gear Lube:
   • Locate Plugs: Identify the vent plug (typically higher on the lower unit) and the drain plug (at the bottom of the gearcase).
   • Remove Vent Plug: Use a flathead screwdriver or socket to loosen and remove the vent plug. This relieves pressure and allows lube to drain freely.
   • Remove Drain Plug: Remove the drain plug, allowing the gear lube to drain completely into the pan. Inspect the lube for metal shavings or milky color (indicating water intrusion).
   • Inspect Plugs: Check the vent and drain plugs for damage. Replace with OEM part 3854539 if worn.
3. Replace the O-Rings:
   • Remove Old O-Rings:
     • For the vent and drain plugs (3855081): Carefully remove the old O-rings from the plugs using a small flathead screwdriver or pick. Avoid scratching the plug surfaces.
     • For the dipstick (3852045): Locate the gear lube dipstick on the stern drive (often near the reservoir). Unscrew or pull out the dipstick and remove the old O-ring.
   • Clean Components: Clean the plugs, dipstick, and surrounding areas with degreaser and rags to remove old lube and debris.
   • Install New O-Rings:
     • Vent/Drain O-Rings (3855081): Slide the new 3855081 O-rings onto the vent and drain plugs, ensuring they seat properly in their grooves. Apply a thin layer of marine grease to prevent sticking and improve sealing.
     • Dipstick O-Ring (3852045): Place the new 3852045 O-ring onto the dipstick, ensuring it fits snugly. Lubricate lightly with marine grease.
4. Reinstall Plugs and Dipstick:
   • Reinstall Drain Plug: Insert the drain plug with the new 3855081 O-ring and tighten securely (hand-tight or to manual-specified torque, typically 10-15 ft-lb). Avoid overtightening to prevent stripping.
   • Reinstall Vent Plug: Insert the vent plug with the new 3855081 O-ring and tighten similarly.
   • Reinstall Dipstick: Insert the dipstick with the new 3852045 O-ring, ensuring it’s fully seated or screwed in as per design.
5. Refill Gear Lube:
   • Fill the Lower Unit: Using a gear lube pump, fill the lower unit through the drain plug hole until lube reaches the vent plug hole or dipstick level. Use Volvo Penta-approved gear lube (e.g., STAR BRITE Synthetic 80w-90).
   • Check Level: Reinstall the vent plug temporarily, then check the dipstick to ensure the lube level is correct. Add more if needed.
   • Secure All Plugs: Ensure the drain, vent, and dipstick are tightly secured.
6. Test and Inspect:
   • Run the Engine: If safe (e.g., with a water source for cooling), run the engine in neutral to circulate the gear lube.
   • Check for Leaks: Inspect the drain, vent, and dipstick areas for leaks after running for a few minutes. Tighten plugs if necessary.

• • Recheck Lube Level: After the first use, recheck the gear lube level with the dipstick and top off if needed.