OBR ME-G4-07D Mercury 75–115 HP standard lower unit with 20-inch shaft
OBR ME-G4-07F Mercury 75–115 HP standard lower unit with 25-inch shaft
OBR ME-G4-20 Mercury Command Thrust lower unit with 20-inch shaft
OBR ME-G4-21 Mercury Command Thrust lower unit with 25-inch shaft
OBR ME-G4-25 Mercury 115 Pro XS lower unit with 20-inch shaft
OBR ME-G4-26 Mercury 115 Pro XS lower unit with 25-inch shaft
OBR ME-G4-30 Mercury 115 Pro XS Command Thrust lower unit with 20-inch shaft
OBR ME-G4-31 Mercury 115 Pro XS Command Thrust lower unit with 25-inch shaft
OBR ME-G4-07D Mercury 75–115 HP standard lower unit with 20-inch shaft
OBR ME-G4-07F Mercury 75–115 HP standard lower unit with 25-inch shaft
OBR ME-G4-20 Mercury Command Thrust lower unit with 20-inch shaft
OBR ME-G4-21 Mercury Command Thrust lower unit with 25-inch shaft
OBR ME-G4-25 Mercury 115 Pro XS lower unit with 20-inch shaft
OBR ME-G4-26 Mercury 115 Pro XS lower unit with 25-inch shaft
OBR ME-G4-30 Mercury 115 Pro XS Command Thrust lower unit with 20-inch shaft
OBR ME-G4-31 Mercury 115 Pro XS Command Thrust lower unit with 25-inch shaft

Mercury 75–115 HP 4-Stroke Lower Unit | Pro XS & Command Thrust

$3,369.00
$3,739.59
$3,369.00
SKU: ME-G4-21-R
Product type: Lower Unit
Please hurry! Only 100 left in stock
Subtotal: $3,369.00

Required for fitment review to confirm compatibility.

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OBR Parts new and remanufactured gearcase options
Designed for select Mercury 75, 90 and 115 HP four-stroke engines
20-inch L and 25-inch XL shaft options
Clearly identified 2.07:1 and 2.38:1 gear ratios
Individual ME-G4 SKU for every listed configuration
OBR two-year limited gearcase warranty
OBR ME-G4-07D Mercury 75–115 HP standard lower unit with 20-inch shaft

Mercury 75–115 HP 4-Stroke Lower Unit | Pro XS & Command Thrust

$3,739.59 $3,369.00
OBR ME-G4-07D Mercury 75–115 HP standard lower unit with 20-inch shaft
OBR ME-G4-07F Mercury 75–115 HP standard lower unit with 25-inch shaft
OBR ME-G4-20 Mercury Command Thrust lower unit with 20-inch shaft
OBR ME-G4-21 Mercury Command Thrust lower unit with 25-inch shaft
OBR ME-G4-25 Mercury 115 Pro XS lower unit with 20-inch shaft
OBR ME-G4-26 Mercury 115 Pro XS lower unit with 25-inch shaft
OBR ME-G4-30 Mercury 115 Pro XS Command Thrust lower unit with 20-inch shaft
OBR ME-G4-31 Mercury 115 Pro XS Command Thrust lower unit with 25-inch shaft

Mercury 75–115 HP 4-Stroke Lower Unit | Pro XS & Command Thrust

$3,739.59 $3,369.00
Product Type: Re-manufactured
HP/Shaft/Years/Ratio: 75/90/115 HP Standard | 20 Inch L | 2.07:1 | 2014–2023

    OBR replacement gearcase for select Mercury 75, 90 and 115 HP four-cylinder four-stroke outboards. This product family covers standard, Command Thrust, 115 Pro XS, and 115 Pro XS Command Thrust configurations, with both 20-inch L and 25-inch XL shaft options.

    Standard 75/90/115 and 115 Pro XS configurations use the listed 2.07:1 gear ratio. Command Thrust and Pro XS Command Thrust configurations use 2.38:1. Each application is available as either a new or remanufactured OBR gearcase under its own ME-G4 SKU.

    Fitment must be determined from the engine serial number, model number, existing gearcase family, shaft length, and gear ratio. Horsepower and model year alone are not sufficient. Product-specific supplier listings currently identify standard and Command Thrust applications through 2023 and Pro XS applications through 2023. Any 2024 order must be confirmed in writing before shipment.

    OBR states that gearcase assemblies ship without lubricant. The correct manufacturer-specified gear oil must be added before operation, and OBR’s break-in and shift-adjustment instructions must be followed. New and remanufactured OBR gearcases are covered by OBR’s published two-year limited warranty, subject to its inspection, installation, and usage requirements.

    • Brand: OBR Parts
    • Product Type: Replacement outboard lower unit / gearcase
    • Compatible Engines: Mercury 75 HP, 90 HP and 115 HP four-cylinder four-stroke
    • Configurations: Standard, Command Thrust, 115 Pro XS and Pro XS Command Thrust
    • Fitment Years: 2014–2023; Pro XS applications 2016–2023
    • Shaft Lengths: 20-inch L and 25-inch XL
    • Gear Ratios: 2.07:1 Standard/Pro XS; 2.38:1 Command Thrust
    • Condition Options: New and remanufactured
    • SKU Family: ME-G4-07D/F, ME-G4-20/21, ME-G4-25/26 and ME-G4-30/31
    • Warranty: OBR two-year limited warranty
    • Important: Engine serial number, shaft length and gear ratio must be verified before ordering
    • 2024 Fitment: Not confirmed; verify before publishing or ordering
    • Select ME-G4-07D or ME-G4-07F only for a verified standard 75/90/115 HP 2.07:1 application.
    • Select ME-G4-20 or ME-G4-21 only for a verified 75/90/115 HP Command Thrust 2.38:1 application.
    • Select ME-G4-25 or ME-G4-26 only for a verified 115 Pro XS 2.07:1 application.
    • Select ME-G4-30 or ME-G4-31 only for a verified 115 Pro XS Command Thrust 2.38:1 application.
    • Use the 20-inch SKU only when the existing engine uses an L-shaft gearcase.
    • Use the 25-inch SKU only when the existing engine uses an XL-shaft gearcase.
    • Match the exact engine serial number and model number.
    • Confirm the existing gear ratio.
    • Confirm the existing gearcase is standard or Command Thrust.
    • Confirm rotation before ordering.
    • Do not order by horsepower alone.
    • Do not assume that all Mercury 75, 90, or 115 HP engines use the same gearcase.
    • Standard and Command Thrust gearcases have different listed ratios and must not be treated as interchangeable.
    • Pro XS and Pro XS Command Thrust require different SKUs.
    • Command Thrust does not mean counter-rotation.
    • Do not advertise counter-rotation for these 16 variants without an exact OBR LH SKU.
    • Confirm whether a propeller or hub change is required when moving between gearcase families.
    • Verify driveshaft, shift-shaft, and propeller-shaft specifications.
    • Fill the gearcase with the manufacturer-required lubricant before use.
    • Adjust idle speed and shift linkage correctly.
    • Installation or use before confirming fitment may affect return and warranty eligibility.
    • Installed or used products are not eligible for a standard Mariners Warehouse return.
    • A 2024 application requires supplier confirmation before shipment.
    • Orders are generally processed within 1–2 business days, Monday through Friday, excluding holidays.
    • Estimated standard delivery is 3–7 business days after processing.
    • Expedited and overnight options may be available at checkout, depending on the destination and product size.
    • Shipping charges are calculated at checkout using the package weight, dimensions, destination and selected delivery method.
    • A tracking number will be emailed after the order ships.
    • Lower units are heavy products and may require special handling or freight service.
    • Delivery times are estimates and may be affected by weather, carrier delays or remote locations.
    • Inspect the package immediately after delivery. Report visible damage and retain the packaging, photographs and tracking information.
    • Confirm the shipping address before completing checkout because changes may not be possible after dispatch.
    • International customers are responsible for applicable customs duties, taxes and import fees.

    Quick Fitment Summary

    Specification Mercury 75–115 HP 4-Stroke Lower Unit | Pro XS & Command Thrust
    Manufacturer / Brand OBR Parts
    Compatible Engine Make Mercury
    Engine Architecture Four-cylinder four-stroke
    Standard and Command Thrust Fitment 75 HP, 90 HP and 115 HP applications listed for 2014–2023
    Pro XS Fitment 115 HP Pro XS and Pro XS Command Thrust applications listed for 2016–2023
    2024 Applications VERIFY BEFORE PUBLISHING — current product-specific supplier listings end at 2023
    Available Configurations Standard, Command Thrust, 115 Pro XS and 115 Pro XS Command Thrust
    Shaft Lengths 20-inch L and 25-inch XL
    Standard / Pro XS Gear Ratio 2.07:1
    Command Thrust Gear Ratio 2.38:1
    Condition Options New and remanufactured
    SKU Families ME-G4-07D, ME-G4-07F, ME-G4-20, ME-G4-21, ME-G4-25, ME-G4-26, ME-G4-30 and ME-G4-31
    Rotation VERIFY BEFORE PUBLISHING — no counter-rotation SKU is identified among the 16 current variants
    Warranty OBR two-year limited warranty for new and remanufactured gearcases
    Gear Oil Not installed for shipment; fill with the engine manufacturer's specified gear lubricant before operation
    Fitment Verification Engine serial number, model number, gearcase family, shaft length and gear ratio must be confirmed
    Core Charge VERIFY BEFORE PUBLISHING — confirm whether a refundable core deposit is included or charged for each SKU

    How to Choose a Mercury 75–115 HP 4-Stroke Lower Unit | Pro XS & Command Thrust

    This OBR Mercury 75–115 HP four-stroke lower-unit family provides new and remanufactured replacement gearcases for select Mercury 75 HP, 90 HP and 115 HP outboards. Available applications include standard Mercury lower units, Mercury Command Thrust lower units, Mercury 115 Pro XS lower units and Pro XS Command Thrust configurations.

    Choose between a 20-inch L or 25-inch XL shaft. Standard and non-Command-Thrust Pro XS configurations use the listed 2.07:1 gear ratio, while Command Thrust configurations use 2.38:1. Every shaft length, gearcase type and condition has a separate ME-G4 SKU.

    Before ordering, confirm your Mercury engine serial number, model number, existing gearcase configuration, shaft length and gear ratio. Horsepower and model year alone are not enough to guarantee fitment. Current product-specific supplier listings cover 2014–2023 standard and Command Thrust applications and 2016–2023 Pro XS applications. A 2024 engine requires written compatibility confirmation before purchase.

    Application / Compatibility Guide

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

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    What Customers Say

    Clear fitment process for 115 HP Pro XS 4-Stroke

    The product details made it simple to verify that this gearcase was the exact match for my 2019 Mercury 115 HP Pro XS. The 2.07:1 gear ratio, 20-inch shaft length, and high-performance housing specs aligned perfectly. Double-check your gear ratio before ordering.
    Travis Whitmore Verified buyer
    October 2023

    Helpful guidance for Command Thrust 90 HP setup

    I appreciated how clearly the Command Thrust options were separated from standard gearcase models. The larger 4.9-inch torpedo housing and 2.38:1 gear ratio made a huge difference on my heavy pontoon boat. Fitment support was very helpful.
    Reginald Thatcher Verified buyer
    June 2023

    Direct bolt-on for Mercury 75 HP 4-Stroke

    The drive shaft splines and mounting bolt pattern lined up without issue on my 2017 Mercury 75 HP 4-stroke. The unit was well-packaged in foam padding. Shifts cleanly and runs quiet after completing the break-in period.
    Soren Caldwell Verified buyer
    September 2022

    Good unit, installation took extra patience

    Matching the engine serial number and gear ratio made ordering straightforward. The lower unit performs well on the water, though removing the protective transport frame and unboxing required extra effort during setup.
    Wesley Vance Verified buyer
    April 2021

    Solid gearcase for 20-inch shaft Command Thrust motor

    Replaced a worn lower unit on my 115 HP Command Thrust outboard. The product listing detailed shaft length and gear ratio parameters clearly, preventing any fitment mistakes. Performance has been solid since day one.
    Derrick Thornton Verified buyer
    August 2019

    Frequently Asked Questions

    Who manufactures these Mercury replacement lower units?
    These replacement gearcases are manufactured or remanufactured under the OBR Parts brand. Mercury is the compatible engine manufacturer, not the manufacturer of the replacement unit.
    Which Mercury engines are covered by this product family?
    The product family covers select Mercury 75 HP, 90 HP and 115 HP four-cylinder four-stroke standard and Command Thrust applications, plus select 115 HP Pro XS and Pro XS Command Thrust applications.
    What model years are confirmed by the product-specific supplier listings?
    The standard and Command Thrust listings currently identify 2014–2023 applications. The 115 Pro XS and Pro XS Command Thrust listings identify 2016–2023 applications.
    Will these lower units fit a 2024 Mercury engine?
    The current Mariners Warehouse page claims 2024 compatibility, but the product-specific supplier listings reviewed for these SKUs end at 2023. A 2024 engine requires written fitment confirmation before ordering.
    What is the difference between the standard and Command Thrust configurations?
    They are different gearcase configurations with different listed gear ratios. The standard configuration uses 2.07:1, while the Command Thrust configuration uses 2.38:1. They should not be treated as interchangeable.
    Does Command Thrust mean counter-rotation?
    No. Command Thrust identifies the gearcase configuration and does not identify propeller rotation. None of the 16 current variants is specifically labeled as a counter-rotation SKU.
    What gear ratio does the standard Mercury 75–115 HP lower unit use?
    The listed standard ME-G4-07D and ME-G4-07F configurations use a 2.07:1 gear ratio.
    What gear ratio does the Command Thrust lower unit use?
    The listed ME-G4-20 and ME-G4-21 Command Thrust configurations use a 2.38:1 gear ratio.
    What gear ratio does the Mercury 115 Pro XS lower unit use?
    The non-Command-Thrust ME-G4-25 and ME-G4-26 Pro XS configurations use 2.07:1. The ME-G4-30 and ME-G4-31 Pro XS Command Thrust configurations use 2.38:1.
    Which shaft lengths are available?
    Both 20-inch L and 25-inch XL configurations are available. The shaft length must match the existing engine and gearcase configuration.
    What is the difference between the new and remanufactured options?
    A new unit is sold as a new OBR gearcase. A remanufactured unit has been rebuilt and supplied under the OBR remanufactured program. Both conditions are covered by OBR's published two-year limited gearcase warranty.
    How do I identify the correct SKU?
    Confirm the engine serial number, model number, standard or Command Thrust configuration, Pro XS status, shaft length, gear ratio and rotation. Do not select a SKU using horsepower and year alone.
    Is the Mercury engine serial number required?
    Yes. The engine serial number should be required at checkout and reviewed before shipment because it provides the strongest available fitment reference.
    Does the lower unit arrive with gear oil installed?
    No. OBR states that gearcase assemblies ship without oil. Fill the unit with the engine manufacturer's specified gear lubricant to the recommended level before operation.
    What warranty is provided?
    OBR publishes a two-year limited warranty for new and remanufactured gearcases. Coverage is subject to OBR inspection and the complete warranty terms, including installation, use, maintenance and return requirements.
    Is a refundable core charge required?
    The Mariners Warehouse product page does not currently disclose a core charge. Confirm the exact core-deposit amount, return deadline, core condition and refund process before ordering.
    What is included with the lower unit?
    The verified included item is one OBR gearcase assembly in the selected SKU and condition. The exact inclusion of the water pump, anodes, mounting hardware, propeller hardware and installation components must be confirmed before publication.
    Should the lower unit be professionally installed?
    Professional marine installation is recommended. Correct lubricant, idle speed, shift linkage adjustment and break-in procedures are important for operation and warranty protection.
    What break-in procedure should be followed?
    Follow OBR's published gearcase instructions: add the required lubricant, set idle speed correctly, adjust shifting, avoid full-throttle starts, vary operating speed, stay below 75 percent throttle for the first five hours and avoid sustained full throttle during the next five hours.
    Can an installed lower unit be returned?
    Mariners Warehouse states that assembled, installed or used products are not eligible for a standard return. Fitment must therefore be confirmed before installation.

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