Volvo Penta Propeller Shaft Oil Seal 3863090 | SX DPS Lower Gearhousing

Volvo Penta 3863090 – Propeller Shaft Oil Seal

• Part Number: 3863090
• Brand: Volvo Penta (OEM Genuine)
• Official Product Type: Oil Seal – Propeller Shaft / Bearing Housing
• System: Lower Gearhousing / Propeller Shaft
• Diagram Position: Item 15 in the SX-A lower gearhousing assembly
• Dimensions: Approx. 44.5 mm O.D. × 30 mm I.D. × 7 mm width
• Supersedes: 3853474, 3858303 (earlier Volvo Penta propeller shaft seal references)
• Aftermarket Cross-References: GLM 85900 / REC3863090
• Weight: Approx. 0.06 lb (25 g)
• Kit Contents: Oil seal only – bearing carrier, O-rings, shims, and gear oil are serviced separately

The 3863090 is a genuine OEM Volvo Penta propeller shaft oil seal used in the lower gearhousing on selected SX and DPS sterndrives. It sits at diagram position 15 in the lower gearhousing assembly, sealing the propeller shaft at the bearing housing to retain gear oil and prevent water or debris from entering the lower unit. Volvo Penta part 3863090 supersedes earlier references 3853474 and 3858303 in supported applications — confirm by your drive’s serial number before ordering.

Compatible Applications

• Volvo Penta SX-A – lower gearhousing, diagram position 15
• Volvo Penta SX-C – lower gearhousing (confirm by serial)
• Volvo Penta SX-R – lower gearhousing (confirm by serial)
• Volvo Penta SX-M – lower gearhousing (confirm by serial)
• Volvo Penta SX-S – lower gearhousing (confirm by serial)
• Volvo Penta DPS-A – lower gearhousing (confirm by serial)
• Volvo Penta DPS-B – lower gearhousing (confirm by serial)
• Volvo Penta DPS-D – lower gearhousing (confirm by serial)
• Volvo Penta FWD-B – lower gearhousing (confirm by serial)
• Volvo Penta FWD-D – lower gearhousing (confirm by serial)
• Related TSK transom / sterndrive configurations where 3863090 is specified – confirm by serial

Serial Number Notice: Fitment depends on the exact drive model, lower gearhousing variant, bearing carrier arrangement, and serial number range. Always confirm 3863090 against your drive’s serial number and lower gearhousing diagram before ordering, especially when replacing earlier references 3853474 or 3858303.

When to Replace

Replace this seal when gear oil leakage is found at the propeller shaft area, when water intrusion has contaminated the gear oil (milky or discoloured oil), when fishing line or debris has cut or damaged the seal lip, when the seal is hardened or torn, when corrosion is found around the seal bore, or whenever the bearing carrier is removed for service. A leaking prop shaft oil seal allows gear oil loss and water ingestion into the lower unit — both can cause rapid lower-unit bearing and gear damage if not addressed.

Service Interval

Inspect the propeller shaft seal area during annual sterndrive service and whenever the lower gearhousing is opened. Replace any time the bearing carrier is removed or the seal shows signs of wear or damage. Proactive replacement during a lower-unit overhaul is strongly recommended to avoid repeat disassembly.

Associated Service Parts

• Volvo Penta Shaft O-Ring 3852565 – SX / DPS forward drive shaft O-ring seal
• Volvo Penta Lower Gear Housing O-Ring 3889786 – SX-A / DPS lower gearhousing O-ring
• Volvo Penta Sealing Ring 851407 – Related SX/DPS sterndrive sealing ring
• Volvo Penta Synthetic Gear Lube 75W-90 1141679 – OEM gear oil for lower unit refill after seal service
• Volvo Penta Gear Lube 80W-90 1141676 – OEM gear oil alternative for lower unit refill
• Volvo Penta Shift Mechanism Sealing Ring 3863085 – Related SX-A / DPS shift mechanism seal
• Volvo Penta Split Pin / Cotter Pin 3885524 – SX-A / DPS-A / DPS-B split pin

Installation Notes

Before installing the new seal, inspect the propeller shaft sealing surface for scoring or corrosion — a damaged shaft surface will cut the new seal lip quickly. Inspect the bearing carrier, seal bore, adjacent O-rings, shims, and gear oil condition at the same time. Press the seal squarely into the bore to the correct installation depth for the specific lower gearhousing — do not hammer directly on the seal face. If the drained gear oil appears milky or water-contaminated, pressure- or vacuum-test the drive after seal replacement before returning the boat to service to confirm all sealing points are sound.

Technical FAQ

Q: What superseded part numbers does 3863090 replace?
A: The 3863090 supersedes earlier Volvo Penta references 3853474 and 3858303 in supported applications. Always confirm the supersession against your exact drive serial number and parts diagram — not all earlier seal configurations are directly interchangeable.

Q: Is this seal drive-specific or engine-size specific?
A: This seal is drive and lower-gearhousing specific, not engine-displacement specific. Fitment is determined by the drive model, bearing carrier, and serial number range — not by the engine attached to it.

Q: My gear oil is milky — will replacing this seal fix the problem?
A: Milky gear oil indicates water ingestion and the lower unit should be serviced promptly. The prop shaft seal is a common entry point, but water can also enter through the lower gearhousing O-ring or other sealing points. Inspect and replace all seals in the lower unit and pressure-test after reassembly. Also drain and refill the gear oil with fresh OEM specification gear lube.

Q: What gear oil should I use after replacing the seal?
A: Refill with Volvo Penta specification gear lube — either Synthetic 75W-90 GL-5 or 80W-90 GL-5 depending on your drive’s specification. Confirm the correct grade in your Volvo Penta drive manual.

Parts Desk Insights

Best Use Case: This is the correct part for customers replacing a leaking or damaged propeller shaft oil seal in the lower gearhousing on SX or DPS sterndrives. Most often ordered alongside the lower gearhousing O-ring and gear oil as part of a complete lower-unit seal service. Customers replacing this seal because of milky gear oil should also replace the lower gearhousing O-ring and pressure-test the drive before putting the boat back in the water.

Common Issues: The most frequent mistake is replacing this seal without inspecting the propeller shaft surface for scoring — a grooved or corroded shaft will cut the new seal lip quickly, causing the same leak to return. The second common issue is stopping at the prop seal without checking the other lower-unit sealing points; if water got in through this seal, it may have entered elsewhere too. Always inspect all lower-unit seals and O-rings while the unit is open, and refill with fresh gear oil after service.