OBR Mercury BigFoot Command Thrust lower unit for 40–60 HP four-stroke
OBR Mercury BigFoot Command Thrust lower unit for 40–60 HP four-stroke

Mercury BigFoot Lower Unit | 40–60 HP 4-Stroke

$2,822.00
$3,132.42
$2,822.00
(-10%)
SKU: ME-G3-05A-N
Product type: Lower Unit

Product Condition: New

Please hurry! Only 100 left in stock
Subtotal: $2,822.00

Required for fitment review to confirm compatibility.

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New and remanufactured OBR replacement gearcases
Six individually verified live SKU configurations
20-inch L and 25-inch XL applications
2 to 3 year OBR limited warranty — terms and exclusions apply
Ships dry; water-pump kit sold separately unless stated
OBR Mercury BigFoot Command Thrust lower unit for 40–60 HP four-stroke

Mercury BigFoot Lower Unit | 40–60 HP 4-Stroke

$3,132.42 $2,822.00
OBR Mercury BigFoot Command Thrust lower unit for 40–60 HP four-stroke

Mercury BigFoot Lower Unit | 40–60 HP 4-Stroke

$3,132.42 $2,822.00
Product Type: New OBR Gearcase
HP/Shaft/Years/Ratio: New | 2001–2007 | 20-inch L | 2.33:1 | ME-G3-05A-N

    The OBR Replacement Lower Unit is a precision-engineered gearcase designed for selected Mercury 40 HP, 50 HP, and 60 HP Inline-4, 4-stroke BigFoot and Command Thrust outboard engines. Engineered specifically for heavy-duty marine service, this replacement unit utilizes the larger 4.25-inch gearcase housing, making it an ideal choice for pontoons, commercial vessels, workboats, and heavy hull applications that demand increased low-end thrust and enhanced maneuverability.

    Built to meet rigorous performance standards, this gearcase features an optimized 2.33:1 gear ratio to deliver maximum torque delivery under heavy workloads. It comes equipped with a heavy-duty 15-spline propeller shaft, ensuring direct compatibility with a wide selection of standard Mercury high-thrust propellers.

    Available in six distinct configurations across both Brand New OBR and OBR Remanufactured build conditions, this series covers selected 2001–2007 and 2008–2026 model years. Depending on your transom setup and year group, units can be configured in either 20-inch (L) or 25-inch (XL) driveshaft lengths. Every unit is manufactured or remanufactured using high-grade internal components and precision-machined housings to ensure smooth power transmission, corrosion resistance, and long-term operating reliability on the water.

    All OBR lower units are backed by a 2-Year OBR Limited Warranty, providing dependable quality and performance for complete peace of mind.

    • Product: OBR aftermarket replacement outboard gearcase / lower unit
    • Compatible engine brand: Selected Mercury applications
    • Horsepower: 40, 50 and 60 HP
    • Engine family: Inline-four, four-stroke BigFoot / Command Thrust
    • Gearcase family: 4.25-inch torpedo/housing family
    • Gear ratio: 2.33:1
    • Propeller shaft: 15-spline application family
    • Rotation: Standard/right-hand application; verify existing unit
    • Driveshaft lengths: 20-inch L and 25-inch XL, depending on SKU
    • Conditions: New OBR or OBR remanufactured
    • Gear oil: Not included; unit ships dry
    • Water pump: Not included unless expressly stated
    • Warranty: Two-year OBR limited warranty; terms and exclusions apply
    • Before ordering, confirm that the engine is a selected Mercury 40, 50, or 60 HP inline-four four-stroke BigFoot or Command Thrust application.
    • Record the complete engine serial number and exact model.
    • Verify the existing 2.33:1 gearcase family.
    • Identify whether the application requires a 20-inch L or 25-inch XL driveshaft.
    • Whenever possible, provide the identifying number from the existing gearcase.
    • OEM reference numbers on this page are compatibility references and do not mean the OBR assembly is manufactured by Mercury.
    • Do not order this product for a standard 1.83:1 Mercury gearcase or an earlier three-cylinder/two-stroke BigFoot application.
    • Fitment is not confirmed by horsepower, model year, or shaft description alone.
    • Mercury used different engine configurations, gear ratios, and gearcase families within overlapping horsepower ranges.
    • Confirm the following details before installation:
    • Complete engine model and serial numbers
    • Existing gearcase or OEM part number
    • 2.33:1 ratio family
    • 4.25-inch housing size
    • Required driveshaft length

    Before shipment:

    • Review the complete engine serial number and model.
    • Confirm inline-four, four-stroke BigFoot/Command Thrust application.
    • Confirm selected OBR SKU.
    • Confirm new or remanufactured condition.
    • Confirm 2001–2007 or verified 2008–2026 year group.
    • Confirm 20-inch L or 25-inch XL driveshaft.
    • Confirm 2.33:1 gearcase family.
    • Confirm any supplied OEM/gearcase reference.
    • Confirm the selected variant price and availability.
    • Confirm whether a core charge applies.
    • Confirm packaged weight and dimensions.
    • Record the fitment-review result in the order.

    After delivery:

    • Inspect the carton for damage before opening.
    • Confirm the received SKU matches the order.
    • Confirm the condition and driveshaft length.
    • Report shipping damage or configuration discrepancies before installation.
    • Do not install a unit that does not match the reviewed order.

    Quick Fitment Summary

    Specification Mercury BigFoot Lower Unit | 40–60 HP 4-Stroke
    Manufacturer OBR
    Product Type New or remanufactured aftermarket replacement lower unit
    Compatible Engine Brand Mercury
    Engine Family BigFoot / Command Thrust inline-four, four-stroke
    Horsepower Selected 40, 50 and 60 HP applications
    Model-Year Groups 2001–2007 or 2008–2026, depending on selected SKU
    Gearcase Family 4.25-inch BigFoot / Command Thrust gearcase
    Gear Ratio 2.33:1
    Propeller Shaft 15-spline
    Rotation Standard / right-hand; verify the existing lower unit before ordering
    Driveshaft Options 20-inch L or 25-inch XL, depending on selected SKU
    Available Conditions New and remanufactured; availability varies by year group and driveshaft length
    2001–2007 SKUs ME-G3-05A-N — New, 20-inch L; ME-G3-05A-R — Remanufactured, 20-inch L; ME-G3-05B-R — Remanufactured, 25-inch XL
    2008–2026 SKUs ME-G3-05C-N — New, 20-inch L; ME-G3-05C-R — Remanufactured, 20-inch L; ME-G3-05D-R — Remanufactured, 25-inch XL
    OEM Reference Numbers 9011G70, 9011G90, 9011J41, 893681T02, 8M0118186, 8M0053765 and 8M0118188; match by selected SKU
    Required Fitment Information Complete engine model and serial number, horsepower, model year, current gearcase/OEM number and driveshaft length
    Not Compatible With Standard 1.83:1 gearcases or earlier three-cylinder/two-stroke BigFoot applications
    Installation Preparation Ships without gear oil; water-pump kit is not included unless explicitly stated
    Warranty Two-year OBR limited warranty; written terms and exclusions apply

    How to Select the Correct OBR BigFoot / Command Thrust Lower Unit

    1. Confirm the engine configuration.
      This listing is for selected Mercury inline-four four-stroke BigFoot/Command Thrust applications. Do not use it for the earlier three-cylinder/two-stroke family.
    2. Record the complete serial number.
      The serial number and exact model are more reliable than horsepower or claimed model year alone.
    3. Confirm the gearcase family.
      Verify the existing 4.25-inch BigFoot/Command Thrust gearcase and 2.33:1 ratio. Do not substitute a standard 1.83:1 gearcase.
    4. Verify driveshaft length.
      Choose 20-inch L or 25-inch XL based on the existing application. Do not determine shaft length from horsepower or transom description alone.
    5. Choose condition.
      Select New or Remanufactured only from the combinations actually offered. The current PDP has no new 25-inch variant.
    6. Submit fitment information before shipment.
      Resolve any mismatch before installation because installed or used merchandise is generally excluded from normal returns.

    Application / Compatibility Guide

    Use CTRL + F or search below to find your engine model

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    What Customers Say

    Perfect replacement for Mercury 60 HP BigFoot

    The product details made it easy to ensure this OBR BigFoot lower unit was the exact replacement for my 2018 Mercury 60 HP 4-Stroke. The 2.33:1 gear ratio, 20-inch shaft, and larger gearcase housing were clearly specified. Verify your exact gear ratio before ordering.
    Brandon Vance Verified buyer
    July 2026

    Clear fitment guidance for 50 HP 4-Stroke pontoon setup

    Replaced the damaged gearcase on my pontoon's Mercury 50 HP 4-Stroke BigFoot motor. The selection guide helped confirm drive shaft length and mounting stud specs. The unit arrived securely bolted in protective packaging.
    Marcus Vance Verified buyer
    March 2025

    Exact match for 40 HP BigFoot gearcase

    The OBR BigFoot documentation made it simple to distinguish this high-thrust lower unit from standard non-BigFoot models. The 2.33:1 ratio was an exact match for my 2015 Mercury 40 HP 4-stroke. Performance has been flawless after the break-in period.
    Tyler Hendricks Verified buyer
    October 2023

    Smooth installation on Mercury 60 HP Command Thrust / BigFoot

    Matching the serial number and gear ratio made the ordering process seamless. Mariners Warehouse fitment assistance quickly confirmed compatibility for my 60 HP 4-Stroke setup. Smooth gear shifting and great thrust once installed.
    Cavin Reynolds Verified buyer
    June 2022

    Sturdy packaging and direct bolt-on fit

    The unit arrived well-padded without any shipping damage. The 25-inch XL shaft BigFoot configuration bolted right up to my Mercury 50 HP 4-Stroke. Make sure to double-check your motor's full serial number and shaft length before buying.
    Zachary Logan Verified buyer
    September 2020

    Frequently Asked Questions

    Will this fit every Mercury 40, 50 or 60 HP outboard?
    No. It is limited to selected inline-four four-stroke BigFoot/Command Thrust applications in the 4.25-inch, 2.33:1 family. Verify the complete model and serial numbers, current gearcase/OEM number and shaft length.
    Is BigFoot the same as Command Thrust?
    They are related high-thrust Mercury gearcase naming families, with Command Thrust used on newer applications. The names alone do not prove interchangeability; verify the exact serial/application and gearcase family.
    How is this different from a standard Mercury lower unit?
    This application uses the BigFoot/Command Thrust 2.33:1, 4.25-inch family. A standard 1.83:1 gearcase is not the same configuration.
    What gear ratio does this product use?
    The listed application family uses a 2.33:1 ratio. Confirm the existing unit before ordering.
    Which driveshaft lengths are available?
    The six live variants include 20-inch L and 25-inch XL remanufactured options, while the current new options are 20-inch only.
    Why are there no new 25-inch variants?
    The current Mariners Warehouse listing and current OBR catalog do not offer ME-G3-05B-N or ME-G3-05D-N. Contact fitment support for current sourcing options.
    What is the difference between new and remanufactured?
    New variants are new OBR aftermarket assemblies. Remanufactured variants are rebuilt by OBR and are identified as remanufactured in the product selector and structured data.
    Is this a genuine Mercury OEM lower unit?
    No. It is an OBR aftermarket replacement gearcase for compatible Mercury applications. OEM numbers are cross-reference identifiers, not a claim that the unit is manufactured by Mercury.
    Is the water pump included?
    No, not unless the selected offer explicitly states otherwise. Plan to install the correct water-pump components during replacement.
    Does the lower unit arrive with gear oil?
    No. OBR states that gearcases ship without oil. Fill with the specified lubricant before operation and follow OBR and Mercury procedures.
    Do I need to return a core?
    Possibly. Core deposits and credits vary. Confirm the selected SKU's charge, eligibility, return deadline, freight responsibility and credit before purchase.
    What warranty applies?
    OBR currently publishes a two-year limited warranty for new and remanufactured gearcases, subject to its written procedure and exclusions. Confirm how Mariners Warehouse administers coverage for your order.
    Can I return the unit after installation?
    Mariners Warehouse's policy generally excludes installed, assembled or used merchandise. Verify fitment before installation and review the current return policy.
    What information should I submit for fitment review?
    Send the complete engine serial number, exact model and horsepower, claimed model year, existing shaft length and any OEM or gearcase number visible on the current unit.

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