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Genuine Mercury Marine OEM Replacement

Genuine Mercury 805726 Drain Screw O-Ring - OEM 8M0204684

The Genuine Mercury 805726 Drain Screw O-Ring is an original equipment sealing component used in select Mercury outboards, MerCruiser sterndrives, Mercury Sport Jet drives, and marine inboard assemblies.

Mercury identifies this component as an O-ring for compatible drain and filler screw applications. It provides a sealing interface between the specified screw assembly and its mating surface.

The original Mercury part number 805726, also referenced as 25-805726, has been superseded by 8M0204684. The newer number is the current Mercury replacement.

This O-ring appears in OEM parts diagrams for select Mercury 6-25 HP outboards, Mercury Racing gear housings, 90-120 HP Sport Jet drives, MerCruiser Alpha One and Bravo drives, and specified marine sea water pump assemblies.

Aftermarket Alternative: For customers seeking a Sierra replacement, see the Sierra 18-7188 Drain Screw O-Ring .

Product Information

• Pro Marine Item Number: 805726
• Manufacturer: Mercury Marine
• Product Type: Drain and Filler Screw O-Ring
• Brand: Genuine Mercury OEM
• Original OEM Part Number: 805726
• Current OEM Replacement: 8M0204684
• Mercury Prefix Reference: 25-805726
• Sierra Cross Reference: 18-7188
• Mallory Cross Reference: 9-76559
• Volvo Penta Cross Reference: 955983
• Application: Specified Drain and Filler Screw Assemblies
• Additional Catalog Applications: Selected Gear Housings and Sea Water Pump Assemblies
• Engine and Drive Families: Mercury Outboard, Sport Jet, MerCruiser Alpha and Bravo
• Condition: New
• Product: OEM Replacement O-Ring

OEM and Cross Reference Numbers

Mercury 805726 is an original equipment O-ring that has been superseded to Mercury 8M0204684. The following numbers identify OEM and aftermarket replacements for the corresponding application.

The Mercury supersession identifies the current factory replacement. Volvo Penta and aftermarket numbers are cross references, not Mercury-issued supersession numbers.

What This Part Is Used For

The Genuine Mercury 805726 O-ring is designed to seal compatible drain and filler screw assemblies. When installed in its specified location, the O-ring helps prevent fluid leakage around the associated fastener.

Mercury parts catalogs also list this O-ring in several marine engine and drive assemblies, including gear housings and sea water pump diagrams. The exact installation location depends on the applicable OEM schematic.

Common Service Applications

• Replacement of compatible drain screw O-rings
• Replacement of compatible filler screw seals
• Mercury outboard gear housing service
• MerCruiser Alpha One gear housing service
• MerCruiser Bravo drive maintenance
• Mercury Sport Jet drive housing service
• Mercury Racing gearcase service
• Specified marine sea water pump repairs
• Replacement of worn, cut, or deteriorated sealing O-rings

Important Fitment Information

Mercury 805726 is not a universal O-ring for every Mercury or MerCruiser drain screw.

The compatibility tables below identify engines and drives whose OEM catalogs reference Mercury part number 805726.

Some applications list this O-ring in gear housing diagrams, while others reference it in drive housing, nozzle/rudder, or sea water pump assemblies.

Always verify the complete engine or drive serial number and the required part number in the applicable OEM schematic.

Compatible Mercury Outboard Applications

Mercury OEM 805726 appears in the following outboard gear housing catalogs. The applications are organized by engine family, with the supplied serial ranges retained.

Mercury 6-15 HP Outboards

Mercury 10 HP Magnum, Marathon, SeaPro and XR

Mercury 20-25 HP Two-Cylinder Outboards

Mercury Racing and Performance Outboards

Mercury Sport Jet Applications

Mercury 805726 appears in the drive housing and nozzle/rudder parts catalogs for selected 90 HP and 120 HP Mercury Sport Jet systems.

The listed Sport Jet applications are based on OEM catalog occurrences. Confirm the specific O-ring location in the applicable drive diagram.

Compatible MerCruiser Sterndrive Applications

Mercury 805726 is referenced in selected MerCruiser Alpha One and Bravo sterndrive parts diagrams.

Alpha One Gen II and Bravo Drives

MerCruiser GM V8 Sea Water Pump Applications

The OEM O-ring also appears in the sea water pump parts diagrams for the following MerCruiser GM 454 and 502 V8 engine families.

MerCruiser Inboard and TowSports Applications

Mercury 805726 is also listed in sea water pump catalog diagrams for selected MerCruiser 7.4L and 8.2L inboard engines.

These applications identify the OEM sea water pump catalogs containing the part. They do not indicate that the O-ring is used in every drain screw on these engines.

Volvo Penta Applications - OEM 955983

Mercury 805726 shares an aftermarket cross-reference relationship with Volvo Penta OEM part number 955983 through Sierra 18-7188.

Sierra identifies 18-7188 as a replacement for both Mercury 805726 and Volvo Penta 955983.

Aftermarket Alternative Available

Pro Marine USA also offers the Sierra aftermarket replacement for customers who prefer an alternative to the Genuine Mercury OEM component.

Common Symptoms of a Damaged Drain Screw O-Ring

An O-ring can deteriorate from age, compression, repeated servicing, or damage during installation. A compromised seal may allow leakage at the associated connection.

• Oil or lubricant leakage around a compatible drain or filler screw
• Visible cuts or cracks in the original O-ring
• Flattened or compressed O-ring material
• Missing or damaged O-ring during maintenance
• Leakage following drain screw removal and reinstallation
• Visible deterioration of the original sealing component

These symptoms may also result from damaged fasteners, sealing surfaces, or other components. Confirm the source of leakage before replacing parts.

Installation and Service Tips

Proper O-ring installation helps prevent damage to the seal and the surrounding assembly. Always follow the Mercury service manual for the applicable engine or drive.

Recommended Installation Practices

• Verify the engine or drive model and complete serial number.
• Confirm the OEM schematic specifies 805726 or 8M0204684.
• Identify the correct drain or filler screw assembly.
• Remove the old O-ring without damaging the sealing groove.
• Inspect the screw and mating surfaces for corrosion or damage.
• Clean the sealing surfaces as directed by the service manual.
• Install the new O-ring without twisting or pinching it.
• Use only manufacturer-approved installation lubricants when specified.
• Follow the required fastener tightening procedure.
• Check for leakage after completing the service.

Key Features and Benefits

• Genuine Mercury OEM: Original equipment replacement component for the specified Mercury applications.
• Updated OEM Number: Mercury 805726 is superseded by 8M0204684.
• Drain and Filler Screw Sealing: Designed for compatible OEM screw assemblies.
• Mercury Outboard Applications: Listed in specified 6-25 HP and performance gear housing catalogs.
• MerCruiser Compatibility: Appears in selected Alpha One and Bravo drive diagrams.
• Sport Jet Applications: Listed in specified 90 HP and 120 HP Sport Jet component catalogs.
• Additional Marine Applications: Referenced in selected inboard and sea water pump diagrams.
• Aftermarket Alternative: Sierra 18-7188 available separately.

Frequently Asked Questions

Is Mercury 805726 a Genuine OEM O-ring?

Yes. Mercury 805726 is an original Mercury Marine O-ring part number. The current Mercury replacement number is 8M0204684.

What replaces Mercury 805726?

Mercury 805726 has been superseded by 8M0204684. This is the current OEM replacement part number.

Is 25-805726 the same as 805726?

Yes. The number 25-805726 is a Mercury part-number format used to identify the same original O-ring.

What is the Sierra replacement for Mercury 805726?

The Sierra aftermarket replacement is Sierra 18-7188 .

Does Mercury 805726 fit Alpha One Gen II drives?

The O-ring appears in specified Alpha One Gen II driveshaft housing and gear housing catalogs. Verify the drive serial number and required O-ring location.

Does this O-ring fit MerCruiser Bravo drives?

Mercury 805726 appears in selected Bravo One, Bravo Two, and Bravo Three gear housing diagrams. Confirm the OEM part number before ordering.

Does Mercury 805726 fit Mercury Sport Jet drives?

Yes. The OEM number appears in selected 90 HP and 120 HP Mercury Sport Jet drive housing and nozzle/rudder parts catalogs.

Does this O-ring fit Mercury 6-25 HP outboards?

It appears in specified gear housing diagrams for several Mercury 6-25 HP outboard families. See the compatibility tables for the listed serial ranges.

Does this O-ring fit Mercury Racing gearcases?

The OEM number appears in selected Mercury Racing IV SSM, VI SSM, and APX gear housing diagrams. Verify the exact model and serial number.

Is Mercury 805726 compatible with Volvo Penta 955983?

Both numbers cross reference Sierra 18-7188. However, Volvo Penta model-specific applications must be confirmed using the appropriate OEM parts diagram.

Is this a complete drain screw assembly?

No. This listing is for the replacement O-ring component, not a complete drain or filler screw.

How do I confirm the correct O-ring?

Locate the original part number in the OEM schematic for your engine or drive. Have the complete model and serial number available when checking compatibility.

Dealer Discounts & Store Policies

Wholesale Marine Parts Pricing

Pro Marine USA supplies Genuine Mercury, OEM, and aftermarket marine engine parts for marine repair shops, dealerships, professional technicians, and retail customers.

Qualified marine businesses can apply for a Pro Marine dealer account to access wholesale pricing on eligible marine parts.

Apply for Dealer Pricing

Shipping Information

• Free shipping on qualifying orders over $100 within the continental United States. Oil and large items are excluded.
• In-stock orders placed before 5:30 PM EST ship the same business day, Monday-Friday.
• Shipping options available through UPS, USPS, and FedEx.
• Typical delivery time is 1-5 business days, depending on destination and shipping service.

30-Day Return Policy

• Eligible returns are accepted within 30 days.
• Parts must be new, unused, and in original packaging.
• Installed parts are not returnable.
• Return authorization is required before returning merchandise.

Need Help Confirming Fitment?

If you are unsure whether Mercury 805726 or its replacement 8M0204684 is correct for your engine or drive, contact Pro Marine USA with your complete engine or drive serial number.

Contact Pro Marine USA or call 941-721-3000.

Searchable Part Numbers

805726, 25-805726, 8M0204684, 25-8M0204684, 18-7188, 9-76559, 955983

Searchable Terms

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