Suzuki SE521 standard-rotation lower unit side view
SE521 90-521-B25F 25-inch Suzuki replacement gearcase
SE521 90-521-B30F 30-inch driveshaft configuration
Suzuki SE521 lower unit propeller-shaft and skeg view
SEI SE521 2.29 ratio standard-rotation gearcase
Suzuki SE521 standard-rotation lower unit side view
SE521 90-521-B25F 25-inch Suzuki replacement gearcase
SE521 90-521-B30F 30-inch driveshaft configuration
Suzuki SE521 lower unit propeller-shaft and skeg view
SEI SE521 2.29 ratio standard-rotation gearcase

Suzuki SE521 Standard-Rotation Lower Unit for DF200, DF225 & DF250

$1,695.00
$1,825.95
$1,695.00
SKU: 90-521-B25F
Product type: Lower Unit
Please hurry! Only 93 left in stock
Subtotal: $1,695.00

Required for fitment review to confirm compatibility.

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Model and serial information reviewed before shippin
25-inch and 30-inch configurations available
Three-year SEI warranty
Suzuki SE521 standard-rotation lower unit side view

Suzuki SE521 Standard-Rotation Lower Unit for DF200, DF225 & DF250

$1,825.95 $1,695.00
Suzuki SE521 standard-rotation lower unit side view
SE521 90-521-B25F 25-inch Suzuki replacement gearcase
SE521 90-521-B30F 30-inch driveshaft configuration
Suzuki SE521 lower unit propeller-shaft and skeg view
SEI SE521 2.29 ratio standard-rotation gearcase

Suzuki SE521 Standard-Rotation Lower Unit for DF200, DF225 & DF250

$1,825.95 $1,695.00
Choose Your SE521 Configuration: 3.6L / 2.29:1 / 25-inch – 90-521-B25F

    The 𝐒𝐮𝐳𝐮𝐤𝐢 𝐒𝐄𝟓𝟐𝟏 𝐥𝐨𝐰𝐞𝐫 𝐮𝐧𝐢𝐭 is a new aftermarket standard-rotation replacement gearcase manufactured by SEI for selected Suzuki DF200, DF225 and DF250 3.6L V6 outboards.

    Available configurations include a 25-inch driveshaft under SKU 90-521-B25F and a 30-inch driveshaft under SKU 90-521-B30F. Both configurations use a 2.29:1 overall ratio with a 12/22 gear-tooth combination.

    The SE521 is designed for verified standard or right-hand rotation TX/TXX applications. It must not be used as a replacement for counter-rotation, left-hand or Suzuki AP-model gearcases.

    Fitment cannot be confirmed using horsepower alone. Before ordering, provide the complete Suzuki engine model, serial number, model year, required rotation and shaft length.

    Quick Fitment Summary

    Specification Suzuki SE521 Standard-Rotation Lower Unit for DF200, DF225 & DF250
    Product New aftermarket replacement gearcase
    Manufacturer SEI
    Engine family Selected Suzuki 3.6L V6 four-strokes
    Models Selected DF200, DF225 and DF250
    Rotation Standard/right-hand only
    Overall ratio 2.29:1
    Gear teeth 12/22
    Shaft options 25-inch and 30-inch
    Model designations Verified TX/TXX applications
    DF200 years 2004–2014
    DF225/DF250 years 2004–current
    Exclusion Does not replace AP models
    25-inch SKU 90-521-B25F
    30-inch SKU 90-521-B30F

    Is the Suzuki SE521 Lower Unit Right for Your Outboard?

    The Suzuki SE521 lower unit is a standard-rotation replacement gearcase for selected 3.6L V6 DF200, DF225 and DF250 outboards. SEI offers this aftermarket Suzuki lower unit in both 25-inch and 30-inch configurations, with a 2.29:1 overall ratio and 12/22 gear-tooth combination.

    The SE521 should be used only for verified standard or right-hand rotation applications. It must not be confused with the SE528 counter-rotation lower unit. Engine position alone does not reliably identify the correct gearcase, especially on twin- or multi-engine boats.

    Before ordering a Suzuki DF200, DF225 or DF250 lower unit, confirm the complete engine model, serial number, model year, required rotation and driveshaft length. The SE521 does not replace Suzuki AP models, and its DF200 application is limited to selected 2004–2014 engines.

    Application / Compatibility Guide

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

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    What Customers Say

    Perfect fit for my DF225

    Ordered the Suzuki SE521 lower unit for my DF225, and the fit was exactly what I needed. The standard rotation setup matched my application, and everything went together cleanly. Very happy with the replacement, and the motor is back on the water.
    Michael R. Verified buyer
    June 2026

    Solid replacement gearcase

    I needed a Suzuki replacement gearcase after damaging my original lower unit. The SE521 lower unit was a good aftermarket option for my Suzuki, and the 2.29:1 setup matched what I needed. Installation went smoothly after confirming the fitment.
    Daniel C. Verified buyer
    May 2026

    Good aftermarket option

    I was looking for an aftermarket Suzuki lower unit instead of rebuilding my damaged gearcase. The SE521 has been a solid replacement so far, and the standard rotation configuration was correct for my setup. Definitely recommend checking your model and shaft length before ordering.
    Robert M. Verified buyer
    April 2026

    30-inch unit fit correctly

    Needed a Suzuki 30-inch lower unit for my outboard and went with the SE521 after checking the engine information. Fitment was straightforward, and the gearcase has been running smoothly. Having the 25-inch and 30-inch options made it easier to get the correct configuration.
    Jason T. Verified buyer
    March 2026

    Back on the water

    My original gearcase was damaged, and I needed a Suzuki outboard lower unit replacement without going through a complete rebuild. The SE521 standard rotation lower unit fit the application well and got the boat back in service. So far, I am very pleased with the replacement.
    Chris B. Verified buyer
    February 2026

    Frequently Asked Questions

    Does the SE521 Suzuki lower unit fit my DF200, DF225, or DF250?
    The SE521 Suzuki lower unit is designed as a replacement for select Suzuki DF200, DF225, and DF250 V6 outboards. Confirmed applications include select Suzuki DF200 applications from 2004–2014 and compatible Suzuki DF225 and DF250 applications from 2004 onward. Always verify the complete engine model, model year, shaft configuration, and serial number before ordering to ensure the SE521 is the correct replacement.
    Is the SE521 a standard-rotation Suzuki lower unit?
    Yes. The SE521 is a Suzuki standard-rotation lower unit designed for compatible TX and TXX applications requiring standard or right-hand rotation. It is not intended for outboards that require a counter-rotation gearcase. Before ordering, verify your engine model, rotation, shaft configuration, and serial number to confirm that the standard-rotation SE521 matches your existing Suzuki lower unit.
    Is the SE521 a new or remanufactured Suzuki lower unit?
    The SE521 is a new aftermarket Suzuki lower unit, not a remanufactured or refurbished OEM gearcase. It is designed as a complete Suzuki outboard lower unit replacement for confirmed DF200, DF225, and DF250 applications. Verify your engine model, model year, shaft length, rotation, and other application details before ordering to ensure the replacement is appropriate for your outboard.
    What gear ratio does the Suzuki SE521 lower unit have?
    The Suzuki SE521 lower unit has a 2.29:1 overall gear ratio, with SEI specifying a 12/22-tooth gear configuration. Matching the correct gear ratio to your engine application is important when selecting a Suzuki replacement gearcase. Before ordering, verify the existing gear ratio and your complete engine model and serial number to help confirm compatibility.
    Is the SE521 available for 25-inch and 30-inch shaft applications?
    Yes. The SE521 is available for confirmed 25-inch (TX) and 30-inch (TXX) applications. Select the correct Suzuki 25-inch lower unit or Suzuki 30-inch lower unit configuration based on your complete engine model and application rather than horsepower alone. Verify the shaft length, model number, serial number, and rotation before ordering to ensure the correct configuration.
    Does the SE521 replace Suzuki AP lower units?
    No. The SE521 application information specifically excludes Suzuki AP models, so it should not be treated as a replacement for an AP gearcase. If your engine model includes an AP designation, verify the correct Suzuki outboard lower unit replacement separately before ordering. Confirm the complete model number, serial number, shaft length, gear ratio, and rotation to help ensure proper application.
    How do I verify the SE521 Suzuki lower unit before ordering?
    Before ordering an SE521 lower unit, verify your complete Suzuki engine model, serial number, model year, standard rotation, and required 25-inch or 30-inch shaft configuration. Do not select a Suzuki replacement gearcase based only on DF200, DF225, or DF250 horsepower. If you are unsure, provide Mariners Warehouse with your engine information so the correct application can be checked before purchase.

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