Mercury Marine OEM Propeller Shaft Oil Seal 66022 | 4.5–9.9 HP & Force Outboard Lower Unit

Mercury Marine OEM Propeller Shaft Oil Seal — Part 66022

• Part Number: 66022
• Full Catalog Number: 26-66022
• Brand: Mercury Marine (Genuine OEM)
• Official Product Type: Seals & Gaskets — Propeller Shaft / Bearing Carrier Oil Seal
• System: Lower Unit / Gearcase — propeller-shaft bearing carrier
• Supersedes: F346118 / 26-F346118 (earlier propeller-shaft seal)
• Qty Required: 1 per applicable gear housing
• GTIN / UPC: 745061168152
• Weight: approx. 0.05 kg

What It Does

The 66022 is the genuine OEM propeller-shaft oil seal used in the bearing carrier of select Mercury, Mariner, and Force small outboard gear housings. It seals around the rotating propeller shaft at the rear of the lower unit, retaining gear lubricant inside the gearcase and preventing water from entering through the prop shaft opening. Mercury gear-housing diagrams identify 66022 specifically as the oil seal at the propeller-shaft bearing carrier location, with one seal required per applicable assembly.

Compatible Applications

Confirm fitment by outboard serial number and gear-housing diagram before ordering. Serial ranges vary across U.S., Canadian, Australian, and European markets within the same HP families.

Mercury / Mariner Outboards

• 4.5 HP
• 6 HP
• 7.5 HP
• 8 HP
• 9.8 HP
• 9.9 HP
• XR10

Force / Chrysler-Derived Outboards

• Force 9.9 HP (select gear housing applications)
• Force 15 HP (select gear housing applications)

Note: This is a Mercury/Mariner/Force small outboard lower unit seal. Do not order for MerCruiser sterndrive propeller shaft applications without first confirming the diagram calls for 66022.

Not sure it fits? Send us your Mercury, Mariner, or Force outboard serial number before ordering.

Related Products

• Mercury Outboard Propeller Shaft Oil Seal 8M0205729 — propeller shaft seal for larger/later Mercury outboard applications
• Mercury Mariner Lower Unit Gear Housing Seal Kit 26-43035A4 — complete lower unit seal kit for applicable Mercury/Mariner gear housings

Part Numbers & Supersession

• 66022 — Current Mercury Marine OEM reference
• 26-66022 — Full Mercury oil-seal catalog format
• F346118 / 26-F346118 — Earlier propeller-shaft seal; superseded by 66022

When to Replace

Replace the propeller-shaft oil seal when:

• Gear lubricant is leaking around the propeller shaft
• Water or milky contamination is found in the lower-unit gear oil at a service interval
• Fishing line or debris has cut or damaged the seal lip
• The bearing carrier is removed for any reason during lower unit service
• The seal is hardened, cut, distorted, or worn during inspection
• A gearcase pressure or vacuum test identifies leakage at the propeller shaft

If water has entered the lower unit, inspect the propeller-shaft surface and bearing-carrier bore condition before installing a replacement seal — a grooved or corroded shaft surface will cause the new seal to leak in the same location.

Service Interval

Inspect at each gear oil change. Replace whenever the bearing carrier is removed, the seal shows any sign of wear or damage, or when a leakage diagnosis confirms the seal is the source. Annual inspection is recommended on outboards operated in saltwater.

Installation Notes

• Inspect the propeller shaft for grooves, corrosion, or fishing-line damage before installing the new seal — a damaged shaft will cut the new seal lip at the same location
• Inspect the bearing carrier bore for corrosion or damage around the seal seat
• Inspect other carrier sealing components while the carrier is removed
• Install the seal in the correct orientation as shown in the Mercury gear-housing diagram
• Follow the applicable Mercury service manual for installation depth, seal lubrication, and carrier torque procedure
• Pressure- and vacuum-test the gearcase after reassembly to confirm the lower unit is sealed correctly before returning the outboard to service

Technical FAQ

Q: What is the difference between 66022 and F346118?
F346118 (also listed as 26-F346118) is the earlier Mercury propeller-shaft seal that was superseded by 66022. If your parts diagram or parts list shows F346118, order 66022 as the current OEM replacement.

Q: Can I use 66022 on a MerCruiser sterndrive?
Verified applications for 66022 are Mercury/Mariner/Force small outboard gear housings. MerCruiser sterndrive propeller shaft seals are different components. Confirm by checking the applicable Mercury parts diagram for your specific assembly before ordering.

Q: My lower unit has milky gear oil — will replacing 66022 fix it?
Milky gear oil indicates water intrusion, and a failed prop-shaft seal is a common cause. However, before installing a new seal, inspect the propeller shaft surface for grooves or damage from fishing line — a damaged shaft will cause the new seal to fail in the same spot. Also pressure-test the gearcase after reassembly to confirm the lower unit is sealed correctly.

Q: How do I confirm the correct serial number range for my outboard?
Mercury serial number ranges for 66022 span multiple markets (U.S., Canadian, Australian, European) within the same HP families. Match your serial number against the Mercury parts diagram for your specific gear housing — ordering by horsepower alone is not sufficient to confirm fitment.

Parts Desk Insights

The 66022 is a straightforward seal, but the two most common issues we see with this part are fishing-line damage and incorrect fitment by horsepower alone. If a customer is replacing this seal because of a gear oil leak, the first thing to check is whether fishing line got wrapped around the prop shaft — it cuts the seal lip and grooves the shaft, and a new seal will fail in the same place if the shaft damage is not addressed first. On fitment: the 66022 covers a range of small outboard gear housings across several markets, and the serial number range is the only reliable way to confirm the right seal for a specific lower unit. Ordering by HP or even by model year without the serial number is where mismatches happen.