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Mercury Racing Lower Unit and Gearcase
Mercury Racing 8M0176859 5.44 Inch XL Gearcase
Mercury Racing 8M0176859 is a 5.44 inch XL gearcase assembly with a 1.60 gear ratio and standard rotation. It is used on Mercury Racing 450R supercharged 4.6L V8 Verado platform applications.
This current Mercury Racing gearcase supersedes 8M0159651. Because complete lower unit assemblies are highly specific to shaft length, gear ratio, rotation, engine family, and serial number, confirm your exact application before ordering.
Compatible Applications
| Brand | Engine / System | Application | Fitment Note |
|---|---|---|---|
| Mercury Racing | 450R Supercharged 4.6L V8 | 5.44 inch XL gearcase, 1.60 ratio, standard rotation | Verify by serial number, shaft length, ratio, and rotation |
| Mercury Racing | High-Horsepower 4.6L V8 Performance Models | Select applications requiring XL shaft and 1.60 standard rotation gearcase | Confirm the OEM parts diagram for your engine serial number |
Important Fitment Note
Always confirm compatibility using your engine serial number, model, existing gearcase number, shaft length, gear ratio, and rotation before ordering. XL, counter rotation, standard rotation, and ratio differences are not interchangeable.
OEM & Cross Reference Numbers
| Current Mercury Racing OEM Number | 8M0176859 |
| Superseded From | 8M0159651 |
| Description | 5.44 inch XL gearcase, 1.60 ratio, standard rotation |
What This Part Is Used For
This is a complete lower unit gearcase assembly used to transfer engine power through the driveshaft and gear set to the propeller shaft. The 1.60 gear ratio and standard rotation configuration are designed for specific Mercury Racing performance setups.
Replacement may be required after gearcase impact damage, internal gear failure, bearing damage, housing damage, or a complete lower unit service decision where assembly replacement is preferred over rebuilding.
Key Features and Benefits
- Genuine Mercury Racing gearcase assembly
- Current part number 8M0176859
- Supersedes Mercury Racing 8M0159651
- 5.44 inch gearcase for high-performance applications
- XL shaft configuration
- 1.60 gear ratio with standard rotation
- Designed for select Mercury Racing 450R and 4.6L V8 performance models
- Best verified by serial number, shaft length, ratio, and rotation
FAQ
What does Mercury Racing 8M0176859 replace?
Mercury Racing 8M0176859 supersedes 8M0159651 for this 5.44 inch XL, 1.60 ratio, standard rotation gearcase application.
Does this fit the Mercury Racing 450R?
This gearcase is used on Mercury Racing 450R supercharged 4.6L V8 applications that require the XL shaft, 1.60 gear ratio, and standard rotation gearcase.
Is this the same as a counter rotation gearcase?
No. This page is for the standard rotation version. Counter rotation gearcases use different part numbers and must be matched to the correct engine and boat setup.
What should I verify before ordering?
Verify your engine serial number, shaft length, rotation, gear ratio, and current gearcase part number. Complete gearcase assemblies are application specific and should not be selected by horsepower alone.
Dealer Discounts & Store Policies
Dealer / Marine Industry Discounts
Are you a marine dealer, technician, boat builder, or industry professional? We offer dealer pricing for qualified marine businesses.
Shipping Policy
- Free shipping on orders over $100 continental U.S.
- Orders ship via UPS, USPS, and FedEx.
- Orders received before 5:30 PM EST ship the same business day.
- Typical delivery time is 1-5 business days.
30-Day Return Policy
- Returns accepted within 30 days of delivery.
- Parts must be new, unused, and in original packaging.
- Installed parts are not returnable.
- Return authorization is required before sending items back.
Need help with a return or order question?
Contact Us
Phone: 941-721-3000
Searchable Terms
Mercury Racing 450R gearcase, Mercury 450R lower unit, Mercury Racing XL gearcase, 5.44 inch gearcase, 1.60 ratio Mercury gearcase, Mercury standard rotation gearcase, Mercury V8 Racing lower unit, 450R standard rotation lower unit
Searchable Part Numbers
8M0176859, 8M0159651, Mercury Racing 8M0176859, Mercury Racing 8M0159651
8M0176859
OEM Mercury Premium Gear Lube
SAE 80W90 Marine Gearcase Lubricant
Mercury Premium Gear Lube 80W90 is engineered to protect marine lower units and sterndrives against wear, corrosion, foaming, and water contamination.
Mercury part number 858058K01 is designed for recreational marine applications requiring SAE 80W90 marine gear lubricant protection.
Compatible Applications
| Application | System Type | Use | Notes |
|---|---|---|---|
| Mercury Outboards | Lower Unit / Gearcase | Gear Lubrication | For compatible recreational outboard applications |
| Mercury Sterndrives | Sterndrive Lower Unit | Gear Lubrication | Compatible with many MerCruiser applications |
| Mariner Outboards | Gearcase | Gear Protection | Select compatible lower units |
| Marine Lower Units | Hypoid Gear Systems | Lubrication & Wear Protection | SAE 80W90 marine gear oil applications |
For racing, surfacing propeller, high-horsepower, or extreme-duty gearcase applications, Mercury also offers Extreme Performance 85W90 Gear Lube.
View Mercury Extreme Performance Gear Lube 85W90
OEM Part Numbers & Product Information
| Type | Details |
|---|---|
| Mercury Part Number | 858058K01 |
| Product Type | Premium Marine Gear Lube |
| Viscosity | SAE 80W90 |
| Container Size | 1 Quart |
| Brand | Mercury Marine |
What This Gear Lube is Used For
Mercury Premium Gear Lube is used to lubricate and protect marine lower units and sterndrives operating in freshwater and saltwater boating environments.
Marine gearcases operate under heavy load and elevated temperatures, making proper lubrication critical for protecting gears, bearings, shafts, and seals from wear and premature damage.
This SAE 80W90 marine lubricant helps reduce friction, resist foaming, minimize corrosion, and provide protection against water intrusion contamination.
Routine lower unit lubricant changes are an important part of preventive marine maintenance and help extend gearcase service life.
Key Features and Benefits
- OEM Mercury Premium Gear Lube
- SAE 80W90 marine gear lubricant
- Designed for Mercury outboards and sterndrives
- Helps protect gears and bearings against wear
- Excellent rust and corrosion protection
- Helps resist foaming and lubricant breakdown
- Provides protection against water contamination
- Ideal for recreational marine lower unit applications
Gear Lube Details
- Brand: Mercury Marine
- Part Number: 858058K01
- Product Type: Premium Marine Gear Lubricant
- Viscosity: SAE 80W90
- Container Size: 1 Quart
- Use: Lower Unit & Sterndrive Lubrication
- Applications: Mercury & Mariner Marine Gearcases
- Environment: Freshwater & Saltwater
FAQ
What is Mercury Premium Gear Lube used for?
This lubricant is used in marine lower units and sterndrives to protect gears, bearings, and internal gearcase components.
What viscosity is this gear lube?
This is SAE 80W90 marine gear lubricant.
When should Mercury Extreme Performance Gear Lube be used instead?
Mercury Extreme Performance Gear Lube is intended for racing, surfacing propeller, and high-performance gearcase applications operating under extreme load and temperature conditions.
Can this be used in saltwater applications?
Yes. Mercury Premium Gear Lube is formulated for both freshwater and saltwater marine environments.
When should lower unit lubricant be changed?
Mercury recommends regular lower unit service intervals as part of routine preventive maintenance.
Dealer Discounts & Store Policies
Dealer / Marine Industry Discounts
Are you a marine dealer, technician, boat builder, or industry professional? We offer dealer pricing for qualified marine businesses.
Shipping Policy
- Free shipping on orders over $100 continental U.S.
- Orders ship via UPS, USPS, and FedEx.
- Orders received before 5:30 PM EST ship the same business day.
- Typical delivery time is 1–5 business days.
30-Day Return Policy
- Returns accepted within 30 days of delivery.
- Lubricants and chemicals must remain unopened and unused for return eligibility.
- Items must be in original packaging and resalable condition.
- Return authorization is required before sending items back.
Need help with a return or order question?
Contact Us
Phone: 941-721-3000
Searchable Terms
858058K01, Mercury gear lube, Mercury Premium Gear Lube, Mercury 80W90, Mercury lower unit oil, Mercury marine gear oil, Mercury sterndrive gear lube, SAE 80W90 marine lubricant, Mercury outboard gear oil, Mercury lower unit lubricant, marine gearcase oil, Mercury gearcase lubricant, Mercury Extreme Performance Gear Lube, Mercury racing gear oil
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