SE318 Magnum Counter Rotation Unit | Johnson Evinrude | 90-318-A | 1.85 Gear Ratio

SE318 Magnum Counter Rotation Unit | Johnson Evinrude | 90-318-A | 1.85 Gear Ratio

$1,645.00
$1,825.95
$1,645.00
(-10%)
SKU: ST-90-318-A
Key Features :
  • Premium Saltwater Corrosion Resistant Finish
  • Precision 1.85:1 Counter Rotation Gearing
  • Backed By 3-Year Fault-Free Warranty
Please hurry! Only 99 left in stock
Subtotal: $1,645.00
SE318 Magnum Counter Rotation Unit | Johnson Evinrude | 90-318-A | 1.85 Gear Ratio

SE318 Magnum Counter Rotation Unit | Johnson Evinrude | 90-318-A | 1.85 Gear Ratio

$1,825.95 $1,645.00
SE318 Magnum Counter Rotation Unit | Johnson Evinrude | 90-318-A | 1.85 Gear Ratio

SE318 Magnum Counter Rotation Unit | Johnson Evinrude | 90-318-A | 1.85 Gear Ratio

$1,825.95 $1,645.00

    Stop letting gearcase failure compromise your twin-engine performance. This Premium Aftermarket Replacement for Johnson and Evinrude Magnum and Mag II outboards delivers balanced, reliable power with a precision 1.85:1 Gear Ratio and a dedicated Counter-Rotation design. Coated in a heavy-duty Corrosion-Resistant Black Finish, this unit is built to outlast harsh marine environments.

    • Twin-Engine Offshore: Essential for balanced steering and matched dual-outboard thrust.

    • High-Torque Performance: Engineered to withstand extreme loads of V6 135HP–300HP engines.

    • Direct Repower Solution: The cost-effective upgrade for replacing obsolete OEM Magnum gearcases.

    • Brand: SEI
    • Part Number: SE318 (90-318-A)
    • Cross-Reference/OEM: Premium Aftermarket Replacement for 5007670
    • Engine Compatibility: Johnson / Evinrude V6 (135HP - 300HP)
    • Year Range: 2002–2012
    • Gear Ratio: 1.85:1
    • Physical Specs: Counter-Rotation, Black Finish, Requires Reusing Original Screens
    • Fits 2002-2012 Johnson/Evinrude outboards (135HP - 300HP) originally equipped with a Magnum or Mag II gearcase.
    • Direct replacement for OEM part number: 5007670.
    • Designed strictly for Counter-Rotation applications requiring a 1.85:1 ratio.
    • Missing Components: Does NOT include an upper driveshaft, shift shaft, water pump, or water intake screens (you MUST reuse your original intake screens).
    • Original Mag Replacement: If you are replacing an original Magnum (not the Mag II), you MUST remove the alignment pins from this new lower unit before installation.
    • 3.4L Water Pump Alert: For 3.4L engines, use OEM kit #5007972 OR reuse your old water tube grommet, o-rings, and plastic housing cover with our standard kit.
    • Verify Your Specs: Always confirm your exact Shaft Length (25" or 30") and upper driveshaft Tooth/Spline Count prior to ordering to prevent incorrect fitment.

    Mariners Warehouse vs Others

    Built to match OEM standards while delivering reliable performance and peace of mind.

    Features

    Mariners Warehouse

    Others
    Performance ✔️ ❌
    Warranty Support Reliable warranty Limited or unclear warranty terms
    Customer Trust Trusted by thousands of marine customers Unverified buyer trust
    Pre-tested before shipping for reliability ✔️ ❌
    OEM performance standards ✔️ ❌
    Simple return process ✔️ ❌

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