ME-G3-09-N OBR Mercury 75/90 HP Optimax 20-inch gearcase
OBR Mercury Optimax lower-unit propeller shaft close-up
Comparison of 20-inch L and 25-inch XL Optimax driveshaft lengths
OBR remanufactured Optimax gearcase identification label
ME-G3-09-N OBR Mercury 75/90 HP Optimax 20-inch gearcase
OBR Mercury Optimax lower-unit propeller shaft close-up
Comparison of 20-inch L and 25-inch XL Optimax driveshaft lengths
OBR remanufactured Optimax gearcase identification label

Mercury Outboard Lower Unit | 75-125 HP | 3-Cyl DFI/Optimax 2004-2018

$2,822.00
$3,132.42
$2,822.00
SKU: ME-G3-13-N
Product type: Lower Unit
Please hurry! Only 100 left in stock
Subtotal: $2,822.00

Required for fitment review to confirm compatibility.

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OBR new and remanufactured gearcase options.
Selected Mercury three-cylinder DFI/Optimax applications.
75, 90, 115 and selected 125 HP configurations.
20-inch L and 25-inch XL shaft options by SKU.
Two-year OBR limited gearcase warranty.
ME-G3-09-N OBR Mercury 75/90 HP Optimax 20-inch gearcase

Mercury Outboard Lower Unit | 75-125 HP | 3-Cyl DFI/Optimax 2004-2018

$3,132.42 $2,822.00
ME-G3-09-N OBR Mercury 75/90 HP Optimax 20-inch gearcase
OBR Mercury Optimax lower-unit propeller shaft close-up
Comparison of 20-inch L and 25-inch XL Optimax driveshaft lengths
OBR remanufactured Optimax gearcase identification label

Mercury Outboard Lower Unit | 75-125 HP | 3-Cyl DFI/Optimax 2004-2018

$3,132.42 $2,822.00
Product Type: New
HP/Shaft/Years/Ratio: 115/125 HP DFI/Optimax | 20-inch L |

    The OBR Mercury Optimax lower unit is a replacement gearcase for selected Mercury three-cylinder DFI/Optimax two-stroke outboards. Depending on the selected SKU, applications include 75 HP, 90 HP, 115 HP, and selected 125 HP engines. Both new and remanufactured gearcase options are available, with 20-inch L and 25-inch XL shaft configurations.

    Each configuration has its own horsepower, shaft-length, and model-year coverage. The ME-G3-09 and ME-G3-10 families cover selected 75/90 HP applications, while the ME-G3-13 and ME-G3-14 families cover selected 115/125 HP applications. Model-year coverage ranges from 2004–2014 or 2004–2018 depending on the exact SKU and condition selected.

    Gearcase assemblies ship without gear oil. The selected unit must be filled with the manufacturer-required marine gear lubricant before operation. Proper installation, idle-speed adjustment, shift adjustment, and the OBR break-in procedure are required. OBR provides a two-year limited warranty for new and remanufactured gearcases, subject to inspection, installation requirements, and the manufacturer’s warranty exclusions.

    • Manufacturer: OBR Parts.
    • Product type: New or remanufactured replacement outboard gearcase.
    • Compatible engine family: Selected Mercury three-cylinder DFI/Optimax two-stroke outboards.
    • Horsepower applications: 75 HP, 90 HP, 115 HP and selected 125 HP applications.
    • Shaft options: 20-inch L and 25-inch XL, depending on SKU.
    • 75/90 HP applications: ME-G3-09-N, ME-G3-09-R and ME-G3-10-R.
    • 115/125 HP applications: ME-G3-13-N, ME-G3-13-R, ME-G3-14-N and ME-G3-14-R; ME-G3-13-R is currently verified for 115 : 2004–2018 or 2004–2014 depending on the selecteHP only.
    • Year ranges: SKU; do not use a universal year range.
    • Gear ratio: Not confirmed in the reviewed SKU data; verify before ordering.
    • Rotation and spline information: Not confirmed in the reviewed SKU data; verify before ordering.
    • Warranty: OBR two-year limited gearcase warranty, subject to the manufacturer’s terms and exclusions.
    • Lubrication: Ships without gear oil; fill and complete the required break-in procedure before normal operation.

    Select the configuration that matches the engine family, horsepower, condition, shaft length, production range, and SKU:

    • ME-G3-09-N: New, Mercury 75/90 HP DFI/Optimax, 20-inch L, 2004–2018.
    • ME-G3-09-R: Remanufactured, Mercury 75/90 HP DFI/Optimax, 20-inch L, 2004–2014.
    • ME-G3-10-R: Remanufactured, Mercury 75/90 HP Optimax, 25-inch XL, 2004–2014.
    • ME-G3-13-N: New, Mercury 115/125 HP DFI/Optimax, 20-inch L. Use 2004–2014 until the supplier resolves its conflicting 2004–2014 title and 2004–2018 FITS block.
    • ME-G3-13-R: Remanufactured, Mercury 115 HP DFI/Optimax, 20-inch L, 2004–2018.
    • ME-G3-14-N: New, Mercury 115/125 HP DFI/Optimax, 25-inch XL, 2004–2018.
    • ME-G3-14-R: Remanufactured, Mercury 115/125 HP DFI/Optimax, 25-inch XL, 2004–2018.

    No engine model suffixes, gear ratios, rotation directions, or spline counts were confirmed in the reviewed supplier listings. Submit the complete engine serial number for final verification.

    Important: Do not order by horsepower, year, or engine position alone.

    • The complete Mercury engine serial number is required.
    • A 20-inch L gearcase must not be substituted for a 25-inch XL configuration.
    • Confirm the existing gear ratio and rotation before purchase.
    • Do not assume a single-engine application is standard rotation or that engine position alone confirms rotation.
    • This listing does not automatically cover carbureted two-strokes, four-strokes, L4 3-jaw/6-jaw units, BigFoot, Command Thrust, Pro XS performance gearcases, TorqueMaster, or other Mercury families.
    • ME-G3-13-N has conflicting published year information and requires serial-based approval.
    • Fill the gearcase with the required marine gear oil before operation.
    • Improper installation, shift adjustment, or break-in can affect warranty coverage.

    Orders are normally processed within 1–2 business days. Please provide the complete engine serial number and confirm the selected SKU, horsepower, shaft length, gear ratio and rotation when known. Missing fitment information may delay order processing. Delivery estimates begin after the order has been processed and shipped.


    • Orders are processed Monday through Friday, excluding national holidays.

    • Orders placed after 2:00 PM, on weekends or on holidays begin processing the next business day.

    • Standard shipping normally takes 3–7 business days after processing.

    • Expedited shipping normally takes 2–3 business days after processing.

    • Overnight shipping may be available and normally takes one business day after processing.

    • Delivery times are estimates and may change because of destination, weather, carrier delays or high shipping volume.

    • Shipping charges are calculated using package weight, dimensions, destination and selected delivery service.

    • The complete shipping charge will be displayed during checkout.

    • A shipping-confirmation email with tracking information will be sent after the order leaves the warehouse.

    • International shipping is available to selected destinations. Customs duties, taxes and import fees are the customer’s responsibility.

    • Check the complete shipping address before placing the order. Incorrect or incomplete addresses may cause delays.

    • Inspect the package immediately after delivery. Report visible damage promptly and retain the original packaging for carrier review.

    • Gearcase assemblies ship without gear oil. Fill the unit with the manufacturer-required marine gear lubricant before installation or operation.

    • Free shipping should not be assumed unless it is specifically displayed in the cart or checkout for the selected destination.

    Quick Fitment Summary

    Specification Mercury Outboard Lower Unit | 75-125 HP | 3-Cyl DFI/Optimax 2004-2018
    Manufacturer OBR Parts
    Compatible engine brand Mercury
    Product family Selected three-cylinder DFI/Optimax two-stroke replacement gearcases
    Horsepower applications 75, 90, 115 and selected 125 HP applications; exact fitment varies by SKU
    Condition options New or remanufactured
    20-inch L shaft SKUs ME-G3-09-N, ME-G3-09-R, ME-G3-13-N and ME-G3-13-R
    25-inch XL shaft SKUs ME-G3-10-R, ME-G3-14-N and ME-G3-14-R
    75/90 HP year coverage 2004-2018 for ME-G3-09-N; 2004-2014 for ME-G3-09-R and ME-G3-10-R
    115/125 HP year coverage ME-G3-13-R is 115 HP only for 2004-2018; ME-G3-14-N and ME-G3-14-R are listed for 115/125 HP 2004-2018
    ME-G3-13-N year note Supplier title states 2004-2014 while its fitment block states 2004-2018; complete serial-number verification is required
    Gear ratio Not confirmed in the published OBR SKU data; verify from the engine serial number and existing gearcase
    Rotation Not confirmed in the published OBR SKU data; verify before purchase
    Warranty OBR two-year limited gearcase warranty; terms and exclusions apply
    Lubrication Ships without gear oil; fill with the manufacturer's required marine gear lubricant before operation
    Required fitment information Complete engine serial number, horsepower, model/year, shaft length, existing ratio and rotation
    Major exclusions Not for carbureted two-stroke, four-stroke, L4 3-jaw or 6-jaw, BigFoot, Command Thrust or unrelated Mercury gearcase families unless separately verified

    How to Choose the Correct Mercury Optimax Lower Unit

    Choosing a Mercury Optimax lower unit requires more than matching the horsepower printed on the cowling. Start with the complete engine serial number, then confirm whether the engine is a three-cylinder DFI/Optimax application. After that, match the existing 20-inch L or 25-inch XL shaft, gear ratio, rotation and the exact OBR SKU.

    For a Mercury 75/90 DFI lower unit, the available configurations on this page include new and remanufactured 20-inch options, plus a remanufactured 25-inch option. Year coverage is not identical: ME-G3-09-N is listed through 2018, while ME-G3-09-R and ME-G3-10-R are listed through 2014.

    Buyers looking for a Mercury 115/125 Optimax gearcase should distinguish the 20-inch ME-G3-13 family from the 25-inch ME-G3-14 family. The remanufactured ME-G3-13-R is currently verified for 115 HP only. Because the published information for ME-G3-13-N contains a year-range conflict, that configuration should receive a serial-number review before shipment. Never substitute a carbureted, four-stroke, L4 or SE205 gearcase solely because its horsepower range appears similar.

    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 OptiMax

    The product specifications made it simple to match the SE216 configuration to my 2012 Mercury 115 HP OptiMax 3-cylinder DFI. The 2.07:1 gear ratio, 20-inch shaft length, and serial number checks were straightforward. Verifying your full serial number before ordering is essential.
    Marcus Sterling Verified buyer
    November 2025

    Helpful DFI-specific fitment support

    I appreciated that the SE216 page specifically separates the 1.5L 3-cylinder DFI applications from standard carbureted models. The Mariners Warehouse team helped confirm my 2008 90 HP DFI configuration prior to shipping. Smooth transaction overall.
    Garrett Lawson Verified buyer
    August 2024

    Direct fit for 2015 Mercury 115 HP Pro XS DFI

    The replacement lower unit arrived securely crated in heavy foam packaging. The drive shaft splines, 20-inch L-shaft, and water pump housing lined up perfectly. Followed the recommended break-in procedure and it has run flawlessly since.
    Brandon Vance Verified buyer
    May 2022

    Solid performance, unboxing took extra effort

    Matching the 2.33:1 gear ratio for my 75 HP OptiMax was very easy with the provided fitment guide. The lower unit performs great on the water, though removing the shipping bracket during setup required a bit of extra time.
    Troy Henderson Verified buyer
    January 2021

    Reliable replacement for 2006 OptiMax 125 HP

    Replaced my damaged gearcase with this SE216 unit on a 25-inch shaft 125 HP OptiMax. The detailed product notes prevented any shaft length or gear ratio missteps. Shift engagement is clean and smooth.
    Derek Callaway Verified buyer
    July 2018

    Frequently Asked Questions

    How do I confirm that this Mercury Optimax lower unit fits my engine?
    Provide the complete Mercury engine serial number and confirm the engine family, horsepower, shaft length, existing gear ratio and rotation. Horsepower and year alone are not enough to confirm fitment.
    Does every variant on this page fit 2004 through 2018 engines?
    No. ME-G3-09-N is listed for 75/90 HP 2004-2018, while ME-G3-09-R and ME-G3-10-R are listed for 2004-2014. The year range also varies among the 115/125 HP configurations.
    What years does ME-G3-13-N fit?
    The supplier title states 2004-2014, while the same page's fitment block states 2004-2018. Use the complete engine serial number for approval and do not rely on the broad year range alone.
    Is this a standard-rotation or counter-rotation lower unit?
    Rotation was not confirmed in the published OBR SKU data reviewed for this page. Confirm the existing rotation and engine serial number before ordering; do not assume rotation from engine position alone.
    How do I choose between the 20-inch L and 25-inch XL shaft?
    Match the replacement to the existing gearcase and engine configuration. Do not substitute a 20-inch L unit for a 25-inch XL application. If uncertain, provide the serial number and a driveshaft or existing-unit measurement.
    What gear ratio or spline count does this lower unit use?
    The exact gear ratio and spline information were not confirmed in the reviewed OBR listings. Verify both details from the existing gearcase and complete engine serial number before purchase.
    Can I use the SE90-205 lower unit instead of this OBR Optimax gearcase?
    Only when the engine serial number, engine type, case design, shaft length, gear ratio and rotation confirm an SE90-205 application. Similar horsepower coverage does not make the two product families interchangeable.
    What engines are excluded from this listing?
    Do not use this listing for carbureted two-strokes, four-strokes, L4 3-jaw or 6-jaw gearcases, BigFoot, Command Thrust, TorqueMaster or other Mercury families unless the exact application is separately verified.
    What is included with the lower unit?
    The order includes one selected OBR gearcase. Water-pump components, anodes, propeller hardware, gaskets and installation hardware are included only when specifically stated in the order confirmation.
    Does the gearcase arrive with gear oil?
    No. OBR states that gearcase assemblies ship without oil. Fill the unit with the engine manufacturer's required marine gear lubricant before operation and follow the OBR break-in instructions.
    What warranty applies to this OBR lower unit?
    OBR publishes a two-year limited warranty for new and remanufactured gearcases. Inspection, freight responsibilities, installation requirements and exclusions apply. The warranty is not three years.
    Can I return the unit, and is a core return required?
    Eligible uninstalled products may be returned under the Mariners Warehouse 14-day policy, subject to authorization, return freight and a 10% restocking fee. Installed or used units cannot be returned. Core requirements are not confirmed on this listing and should be verified before purchase.

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