Mercury Outboard Propeller Shaft Oil Seal - 8M0205729
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The Mercury MerCruiser Quicksilver 8M0205729 is a genuine Mercury Marine OEM propeller shaft oil seal used in select Mercury, Mariner, and MerCruiser lower-unit gearcase assemblies. This seal is installed in the bearing carrier area to help retain gear lubricant inside the lower unit while helping keep water, salt, and debris out of the gearcase.
It is commonly used during lower-unit reseal work, bearing carrier service, propeller shaft service, and gearcase leak repairs where the factory parts diagram calls for 8M0205729 or the earlier 26-70081 reference.
Key Features
- Genuine Mercury Marine OEM oil seal.
- Mercury part number: 8M0205729.
- Mercury category-style formatting: 26-8M0205729.
- Supersedes earlier Mercury reference 26-70081.
- Propeller shaft / bearing carrier sealing application where specified.
- Helps retain lower-unit gear oil.
- Helps prevent water intrusion into the gearcase.
- Listed dimensions: 1.754 in. OD x 1.185 in. ID x 0.360 in. width.
- Metric reference: 45 mm OD x 30 mm ID x 9.1 mm width.
- Commonly cross-referenced with Sierra, GLM, and Honda seal references where applicable.
Engine Compatibility
Common application context includes select Mercury and Mariner outboard gearcases where the factory lower-unit diagram calls for 8M0205729, including:
- Select Mercury / Mariner 30 HP through 150 HP outboard applications where specified.
- Select 75 HP, 80 HP, 90 HP, 100 HP, 115 HP, 125 HP, and 150 HP gearcase configurations where the parts diagram confirms this seal.
- Select 2-stroke and 4-stroke lower-unit bearing carrier applications where specified.
- Select Honda outboard gearcase applications only where the factory parts chart confirms the matching seal reference.
Use this oil seal only where the Mercury, Mariner, MerCruiser, or applicable OEM parts diagram specifically calls for 8M0205729, 26-8M0205729, or a verified replacement for 26-70081.
Serial Number Fitment Notice
Confirm fitment by engine serial number, horsepower, gearcase style, propeller shaft size, bearing carrier layout, seal quantity, and factory lower-unit diagram before ordering. Mercury and Mariner outboards can use different carrier seals across similar horsepower ranges depending on year, gear ratio, case size, shaft diameter, and production range.
When This Part Needs Replacement
Replace this seal if gear oil is leaking from the propeller shaft area, water is entering the lower unit, the gear oil appears milky, fishing line has damaged the seal lip, or the bearing carrier has been removed for service. It should also be replaced during lower-unit reseal work, propeller shaft repairs, gearcase rebuilds, or any service where the seal is removed or disturbed.
Installation Notes
Inspect the propeller shaft sealing surface before installation. A grooved, pitted, rusty, bent, or rough shaft can damage the new seal lip and allow the leak to return. Clean the bearing carrier bore and install the seal squarely using the correct seal driver or a properly sized installer.
Lightly lubricate the sealing lip with clean gear oil or marine grease before installation. Confirm seal orientation before pressing it into place, especially when multiple seals are installed back-to-back in the carrier. After service, pressure-test and vacuum-test the lower unit before refilling with gear lubricant.
Alternate/Superseded Part Numbers
- 8M0205729 — Mercury OEM part number
- 26-8M0205729 — Mercury category-style catalog formatting
- 26-70081 — superseded Mercury reference
- Sierra 18-2053 — aftermarket cross-reference; verify by gearcase diagram
- GLM 85530 — aftermarket cross-reference; verify by gearcase diagram
- Honda 91255-ZW1-003 — cross-reference; verify by engine model and lower-unit diagram
Parts Desk Insight
Propeller shaft seals are critical lower-unit service parts. A leaking outer seal can let water into the gearcase, contaminate the lubricant, and damage bearings, gears, and shafts. When replacing this seal, inspect the prop shaft for fishing-line cuts, check the carrier O-ring and related seals, and always pressure/vacuum test the gearcase before returning the engine to service.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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