OMC Cobra outboard lower unit on a white speedboat cruising on blue water

OMC Cobra Lower Unit

Compare SE109 standard-rotation and SE117 counter-rotation lower units for selected 1986–1993 dog-clutch OMC Cobra sterndrives. Confirm the original drive family and rotation before ordering.

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3 Year Warranty

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3 Year Warranty

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3 Year Warranty

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3 Year Warranty

Find replacement OMC Cobra sterndrive lower units for 1986-1993 OMC Cobra sterndrive applications. Built as durable aftermarket replacements for the OMC Cobra lower gearcase, these units restore proper shifting and power transfer for your sterndrive-powered boat.

Each OMC Cobra lower unit is manufactured to fit OEM specifications, helping you avoid the high cost and long wait of hard-to-find original OMC Cobra parts. Find the correct gear ratio and configuration for your 1986-1993 OMC Cobra sterndrive below.

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  • OMC Cobra Sterndrive Lower | SE109 | 1986-1993 Standard

    OMC Cobra Sterndrive Lower | SE109 | 1986-1993 Standard SKU: ST-90-109-02

    $1,195.00
    $1,326.45
    $1,195.00
    Restore reliable shifting and maximum propulsion to your vessel with this Premium Aftermarket Replacement for OMC Cobra lower units. Engineered with a heavy-duty Dog Clutch mechanism that shifts directly in the lower, this SE109 unit delivers precise engagement and rugged durability for consistent marine...
    $1,195.00
    $1,326.45
    $1,195.00
  • OMC Cobra Lower | SE117 | Counter Rotation 86-93

    OMC Cobra Lower | SE117 | Counter Rotation 86-93 SKU: ST-1

    $1,395.00
    $1,548.45
    $1,395.00
    Stop overpaying for obsolete original equipment and restore smooth, efficient shifting to your sterndrive with this Premium Aftermarket Replacement for OMC Cobra lower units. Built with Heavy-Duty marine-grade materials, this unit is engineered to meet or exceed OEM specifications, ensuring reliable power transfer and...
    $1,395.00
    $1,548.45
    $1,395.00

How to Choose an OMC Cobra Lower Unit?

The year range alone does not confirm fitment. Before selecting an OMC Cobra replacement lower unit, identify the original drive family, shift design, rotation and case configuration. The SE109 and SE117 in this collection are intended for selected 1986–1993 dog-clutch OMC Cobra sterndrives that shift in the lower unit. They should not be selected for an OMC Stringer, King Cobra or later OMC/Volvo Joint Venture drive.

The SE109 is the standard-rotation option, while the SE117 is the counter-rotation option for applicable twin-engine installations. Do not determine rotation only from the engine’s port or starboard position. Verify the existing gearcase and propeller rotation before ordering. The SE109 also does not replace certain four-cylinder applications equipped with a 4-1/4-inch bullet-diameter case, so compare the existing housing with the exact product application information.

Check the drive model, original gearcase number, OE reference and any available serial or application information. The verified SEI MPN is 90-109-02 for the SE109 and 90-117-02 for the SE117. The SE109 uses a 1-1/4-inch propeller shaft and requires the appropriate new propeller thrust washer. Review the exact product listing to confirm which installation components are included or must be purchased separately.

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Standard vs Counter-Rotation OMC Cobra Lower Units

Rotation must match the existing drive and propeller setup. Standard and counter-rotation lower units are not interchangeable, and rotation should not be selected only from the side of the boat on which the drive is installed.

The SE109, MPN 90-109-02 and OE reference 0985586, is the standard-rotation option for applicable OMC Cobra installations. Before ordering, confirm the original drive family and case configuration. This replacement uses a 1-1/4-inch propeller shaft and requires the applicable new propeller thrust washer.

The SE117, MPN 90-117-02 and OE reference 0985497, is the counter-rotation option for applicable twin-engine installations. Verify the existing gearcase and propeller rotation, and review the exact product listing to confirm which installation components are included or required separately.

Do not choose the SE117 simply because a drive is installed on a particular side of the boat. Confirm the original gearcase, propeller rotation and product application before ordering.

New vs Remanufactured OMC Cobra Lower Units

The current collection appears to contain new aftermarket SEI Marine replacement lower units rather than remanufactured original OMC gearcases. Confirm the published condition and warranty on each listing before launch.

New aftermarket Remanufactured
Manufactured as a replacement assembly Rebuilt from a serviceable used core
Current collection products appear to be SEI Marine replacements No remanufactured unit is currently shown in this collection
Usually does not require a customer core unless stated A core return or deposit may apply
Manufacturer and MPN should appear on the PDP Rebuilder and replaced components should appear on the PDP
Warranty must be shown on the exact listing Warranty must be shown on the exact listing
Installation items must still be confirmed Rebuild scope and testing must be confirmed

Do not imply that new aftermarket and remanufactured units have identical construction, included components, core requirements or warranty coverage.

OMC Cobra Sterndrive Lower Unit Replacements

Standard and Counter-Rotation Replacement Gearcases

This collection includes SEI Marine replacement lower units for 1986–1993 OMC Cobra sterndrives that use a dog-clutch gearcase and shift in the lower unit. Standard- and counter-rotation options are available. Verify the original drive before ordering.

Standard-Rotation Lower Unit

  • SE109 | 90-109-02 – 1986–1993 OMC Cobra, Standard Rotation
  • Replaces OE 0985586
  • Dog-Clutch, Lower-Shift Gearcase

Counter-Rotation Lower Unit

  • SE117 | 90-117-02 – 1986–1993 OMC Cobra, Counter Rotation
  • Replaces OE 0985497
  • For Counter-Rotating Twin-Engine Applications

Compatibility Requirements

  • 1986–1993 Lower-Shift Cobra Drives
  • Excludes King Cobra
  • Excludes Joint Venture Drives
  • SE109 Excludes 4-Cylinder 4-1/4-Inch Cases

Need Help Finding the Right OMC Cobra Lower Unit?

Send us the drive model, serial number, original OE number and required rotation. Our marine-parts specialists can help verify whether the SE109 or SE117 is the correct replacement for your OMC Cobra sterndrive.
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What Customers Say

Fit My 1990 Cobra Perfectly

Been putting off replacing my OMC Cobra lower unit (MPN 90-109-02) for months because of OEM pricing, finally pulled the trigger on this one. Standard rotation, matched my original gearcase exactly, and installation was straightforward once I had the right thrust washer on hand. Running strong a few months in, no leaks or noise issues.
Justin Parker Verified buyer
January 2026

Good Replacement, Just Verify Your Case First

My 1988 Cobra sterndrive needed a standard-rotation unit and this SE109 (MPN 90-109-02) matched up correctly. I called before ordering just to confirm the case configuration since I know OMC Cobra drives aren't all identical, and that extra step made the install go smooth. Solid build quality for the price.
Rebecca Sanders Verified buyer
February 2026

Exactly What My Twin-Engine Setup Needed

Running twin engines on my boat meant I needed a proper counter-rotation unit, not just something that looked similar. This SE117 (MPN 90-117-02) matched my existing gearcase and propeller rotation correctly — learned early on not to guess rotation based on engine side, so I checked the actual prop first. Installed without issues and it's been reliable since.
Gregory Hayes Verified buyer
March 2026

Correct Counter-Rotation Fit, No Surprises

Ordered this SE117 (MPN 90-117-02) after confirming my prop rotation against the listing specs, and it was exactly right. Fits cleanly into the 1986–1993 Cobra range like advertised. Appreciate that it's clearly built as a dedicated counter-rotation unit rather than a generic option, made the buying decision easy.
Diana Coleman Verified buyer
April 2026

Solid Counter-Rotation Unit, Double-Check Before Ordering

Almost ordered the standard-rotation version before realizing my setup needed counter-rotation — glad I checked the gearcase first. Once I had the right part number for the SE117 (MPN 90-117-02), this dropped in fine on my Cobra sterndrive. Been a few months now and it's holding up well under regular use.
Marcus Fields Verified buyer
May 2026

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Frequently Asked Questions

How do I select the correct OMC Cobra lower unit?

Start by confirming that the original drive is a selected 1986–1993 dog-clutch OMC Cobra that shifts in the lower unit. Then verify rotation, case configuration, original part reference and the exact SEI product application. Year alone does not confirm fitment.

Are these OMC Cobra lower units new or remanufactured?

The current SE109 and SE117 listings appear to represent new aftermarket SEI Marine replacement units, not remanufactured original OMC gearcases. Confirm the condition field on the exact product page before ordering.

What gear ratio do I need for an OMC Cobra lower unit?

Do not select these units from a generic gear-ratio assumption. The verified SE109 and SE117 product information identifies application, rotation and OE references but does not provide a universal ratio for every installation. Confirm the complete drive configuration using the appropriate service or application information.

What are the signs of a failing OMC Cobra lower unit?

Possible warning signs include contaminated gear lubricant, visible metal in the lubricant, lubricant leakage, abnormal gear noise, difficult engagement, repeated loss of gear or impact damage. These symptoms can have more than one cause, so the drive should be inspected before replacement is ordered.

When is a counter-rotation OMC Cobra lower unit required?

The SE117 counter-rotation unit is intended for applicable twin-engine installations that already require that rotation. Do not select it solely from the engine’s port or starboard position; verify the existing gearcase and propeller rotation.

How should an OMC Cobra lower unit be protected in saltwater?

Inspect the housing and protective finish regularly, maintain the correct anodes, repair coating damage appropriately and follow the applicable flushing and maintenance procedures. Anode material and maintenance requirements must match the boat’s operating environment and drive setup.

What warranty applies to these replacement lower units?

SEI publishes warranty coverage for qualifying assembled drives and lower units, subject to written terms, exclusions and claim procedures. Mariners Warehouse should show the applicable warranty on each product page and confirm that the exact unit qualifies before making a collection-wide warranty claim.

Should the lower unit be pressure tested after installation?

A leak test may be appropriate following service or installation, but the correct procedure and pressure limits must come from the applicable service information. Do not use a universal internet pressure value, as an incorrect procedure can damage seals or produce misleading results.

What gear lubricant should be used?

Use lubricant that meets the specification for the exact OMC Cobra drive and service application. Fill level, drain-and-fill procedure and inspection interval should follow the applicable service information. Do not assume that the replacement unit arrives filled with lubricant unless the listing explicitly confirms it.

Can I install an OMC Cobra lower unit myself?

Installation requires correct drive identification, shift-system setup, sealing, lubrication, fastener procedures and propeller-hardware selection. The SE109 also requires the applicable new propeller thrust washer. If these procedures are unfamiliar, professional installation is advisable.

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