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Suzuki Outboard Lower Unit

Shop new aftermarket Suzuki outboard lower unit replacements for selected DF200, DF225 and DF250 applications. Compare SE521 standard-rotation and SE528 counter-rotation gearcases in 25- and 30-inch configurations.

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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

Shop aftermarket Suzuki outboard lower units (gearcases), engineered as direct-fit replacements for Suzuki 4-stroke outboard engines. Whether you're dealing with a stripped gear, worn bearing, or impact damage from a submerged obstacle, our Suzuki lower unit replacements restore correct gear ratio and smooth shifting so your outboard runs like new.

Each Suzuki gearcase is built to OEM fit and performance standards, available in the shaft length and rotation configuration your engine requires. Match your Suzuki outboard's HP range and model year to find the correct replacement lower unit below, backed by warranty coverage for peace of mind on the water.

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  • Suzuki SE521 standard-rotation lower unit side viewSE521 90-521-B25F 25-inch Suzuki replacement gearcase
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    Suzuki SE521 Standard-Rotation Lower Unit for DF200, DF225 & DF250 SKU: 90-521-B25F

    $1,695.00
    $1,825.95
    $1,695.00
    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...
    $1,695.00
    $1,825.95
    $1,695.00
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  • Suzuki SE528 counter-rotation lower unit side viewSEI SE528 2.29 ratio counter-rotation lower unit
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    Suzuki SE528 Counter-Rotation Lower Unit for DF200, DF225 & DF250 SKU: 90-528-B25F

    $1,895.00
    $2,070.15
    $1,895.00
    The Suzuki SE528 counter-rotation lower unit is a new aftermarket replacement gearcase manufactured by SEI for selected Suzuki DF200, DF225 and DF250 3.6L V6 outboards requiring counter or left-hand rotation. Available configurations include a 25-inch driveshaft under SKU 90-528-B25F and a 30-inch driveshaft under...
    $1,895.00
    $2,070.15
    $1,895.00
    Quick add
    Close

How to Choose the Correct Suzuki Lower Unit

Choosing a Suzuki lower unit starts with identifying the complete engine model and existing gearcase—not simply matching horsepower. Selected DF200, DF225 and DF250 applications can differ by rotation, model designation and 25- or 30-inch shaft configuration.

Begin with the engine model and serial number. Next, confirm whether the application is standard rotation or counter rotation and whether the model designation corresponds to a supported TX/TXX or ZX/ZXX configuration. Check the current gearcase or OE number when available.

Compare those details with the exact application information on the SE521 or SE528 product page. If any identifier is missing, the model includes AP, or rotation is uncertain, request a fitment check before ordering.

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Application / Compatibility Guide

Search your engine model, or open the full guide below.

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Standard vs Counter-Rotation Suzuki Lower Units

Standard and counter-rotation gearcases are built for different propeller-rotation requirements. In this collection, the SE521 is the standard-rotation family for supported TX/TXX applications, while the SE528 is the counter-rotation family for supported ZX/ZXX applications.

Do not select rotation from engine position alone. Verify the complete engine model, serial number, existing gearcase and propeller rotation before choosing a replacement. A standard and counter-rotation gearcase may look similar while using different internal configurations.

New Aftermarket Suzuki Lower Units

The SE521 and SE528 products currently available in this collection are new aftermarket replacement gearcases manufactured by SEI Marine. They are not genuine Suzuki OEM assemblies or remanufactured units.

New Aftermarket SEI OEM / Remanufactured Alternatives
Sold in new aftermarket condition May be a new Suzuki factory assembly or restored from a serviceable core
Manufactured by SEI Marine Manufactured by Suzuki or processed by a rebuilder
Review the exact listing for core requirements A core return or refundable deposit may apply to remanufactured units
SEI warranty terms shown on the exact product page OEM, dealer or rebuilder warranty terms vary
Confirm the configuration and included components Confirm the condition, replaced parts, testing and included components

Review the individual product page for the exact configuration, included components, availability, warranty and fitment information. Do not assume that aftermarket, OEM and remanufactured options have the same price, included parts, core policy, return requirements or warranty.

Suzuki Outboard Lower Unit Replacements

SEI Replacement Gearcases for Selected DF200, DF225 and DF250 Outboards

This collection brings together complete new aftermarket SEI lower units for selected Suzuki DF200, DF225 and DF250 3.6L V6 outboards. The SE521 family covers supported standard-rotation TX and TXX applications, while the SE528 family covers supported counter-rotation ZX and ZXX applications. Available configurations include 25-inch and 30-inch shaft options. SEI lists overall 2.29 reduction for the SE521 and SE528 families, but ratio alone should not be used to confirm fitment. Match the complete engine model, serial number, shaft configuration and rotation to the exact product application.

Standard-Rotation SE521

  • Selected DF200 TX/TXX applications
  • Selected DF225 TX/TXX applications
  • Selected DF250 TX/TXX applications
  • 25-inch MPN: 90-521-B25F
  • 30-inch MPN: 90-521-B30F

Counter-Rotation SE528

  • Selected DF200 ZX/ZXX applications
  • Selected DF225 ZX/ZXX applications
  • Selected DF250 ZX/ZXX applications
  • 25-inch MPN: 90-528-B25F
  • 30-inch MPN: 90-528-B30F

Need Help Finding the Right Suzuki Lower Unit?

Send the complete Suzuki engine model, serial number, model year, shaft configuration and required rotation before ordering. Include the current gearcase or OE number and clear photos of the engine ID plate when available.
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What Customers Say

SE521 selection was easy to understand

The product information made it easy to compare the SE521 lower unit with the counter-rotation option. The shaft-length and rotation notes clearly showed what needed to be verified for a Suzuki DF225 before ordering. This is a helpful example of how a Suzuki outboard lower unit listing should guide the buyer.
Liam Smith Verified buyer
March 2024

Clear information for a DF200 replacement

I was researching a replacement gearcase for a Suzuki DF200 and found the SE521 product details straightforward. The listing explained that this is a new aftermarket Suzuki lower unit manufactured by SEI Marine, rather than an OEM or remanufactured assembly. The fitment reminders were especially useful.
Noah Johnson Verified buyer
August 2024

Helpful 25-inch shaft guidance

Finding a 25-inch Suzuki lower unit can be confusing when similar engines use different configurations. The SE521 page made the shaft length, standard rotation and compatibility checks easy to follow. I would still confirm the engine model and serial number before purchasing, as the listing recommends.
Oliver Williams Verified buyer
January 2025

Good aftermarket option for comparison

The SE521 lower unit gave me a clear new-aftermarket option to compare with a genuine Suzuki OEM gearcase. I appreciated that the page did not treat horsepower alone as proof of fitment and asked buyers to verify rotation, shaft length and engine information first.
James Brown Verified buyer
May 2025

Useful details for a 30-inch application

I was looking into a 30-inch replacement lower unit for a Suzuki DF250. The SE521 information clearly separated standard rotation from the SE528 counter-rotation family and explained the need to check the exact application. That comparison removed much of the guesswork.
Elijah Jones Verified buyer
September 2025

Counter-rotation option clearly identified

The SE528 counter-rotation lower unit was clearly distinguished from the standard-rotation SE521. That matters on a multi-engine Suzuki setup because engine position alone should not determine the required rotation. The reminder to verify the current gearcase and propeller rotation was valuable.
Olivia Miller Verified buyer
November 2025

Helpful comparison for a twin-engine setup

I was comparing Suzuki lower-unit replacement options for a twin-engine DF225 installation. The SE528 page explained the counter-rotation configuration without implying that every DF225 uses the same gearcase. The model, serial-number and shaft-length checks made the selection process feel much safer.
Emma Davis Verified buyer
February 2026

Important AP-model warning was visible

The most useful detail on the SE528 lower unit listing was the warning about excluded AP applications. Many Suzuki DF200, DF225 and DF250 listings focus only on horsepower, so seeing that limitation before ordering would help prevent an incorrect gearcase purchase.
Amelia Wilson Verified buyer
April 2026

Good explanation of aftermarket condition

The SE528 product information clearly stated that the unit is a new aftermarket gearcase manufactured by SEI Marine. It did not present it as a genuine Suzuki OEM assembly or a remanufactured lower unit. That distinction made the product comparison easier to understand.
Charlotte Taylor Verified buyer
June 2026

Fitment-first buying experience

The collection helped me understand the difference between the SE521 standard-rotation and SE528 counter-rotation Suzuki outboard lower units. Instead of asking buyers to choose by horsepower alone, it highlighted rotation, 25-inch or 30-inch shaft length, engine model and serial verification.
Sophia Anderson Verified buyer
July 2026

Helpful Guides

Explore guides and tips related to this collection.

Split comparison of standard rotation vs counter-rotation boat propeller spin direction for Suzuki SE521 and SE528 lower units

Suzuki SE521 vs SE528: Standard vs Counter-Rotation Lower Units

Suzuki SE521 vs SE528: Standard vs Counter-Rotation Lower Units | Mariners Warehouse Suzuki Fitment Guide SE521 vs SE528 Standard vs...

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Suzuki DF200, DF225 and DF250 outboard lower unit gearcases arranged side by side for compatibility comparison

Suzuki DF200, DF225 & DF250 Lower Unit Compatibility Chart

Suzuki DF200, DF225 & DF250 Lower Unit Compatibility Chart | Mariners Warehouse Mariners Warehouse — Fitment Guide Suzuki DF200, DF225...

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Before and after comparison of a worn Suzuki lower unit versus a rebuilt refurbished Suzuki lower unit gearcase

Suzuki Lower Unit Rebuild vs Replacement: Cost, Damage & Fitment

Suzuki Lower Unit Rebuild vs Replacement: Cost, Damage & Fitment | Mariners Warehouse Suzuki Fitment Guide Suzuki Lower Unit Rebuild...

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Frequently Asked Questions

How do I identify the correct Suzuki lower unit?

Start with the complete engine model and serial number, then confirm the model year, shaft configuration, rotation and current gearcase or OE number. Match those identifiers to the exact SE521 or SE528 product application before ordering.

Is horsepower enough to confirm Suzuki lower-unit fitment?

No. Selected DF200, DF225 and DF250 engines can use different gearcases based on the complete model designation, shaft configuration and rotation. Horsepower should be treated as an initial filter, not final fitment confirmation.

What is the difference between the Suzuki SE521 and SE528?

The SE521 is the standard-rotation family for supported TX/TXX applications. The SE528 is the counter-rotation family for supported ZX/ZXX applications. Verify the full engine and gearcase identification because the two families are not interchangeable selections.

How do I choose between a 25-inch and 30-inch lower unit?

Match the shaft configuration shown for the complete engine model and current gearcase. Do not estimate shaft length from boat size or appearance; select the exact 25- or 30-inch SKU listed for the verified application.

What gear ratio do the SE521 and SE528 use?

SEI lists an overall 2.29 reduction with a 12/22 gear-tooth combination for the SE521 and SE528 families. Ratio alone is not enough to confirm fitment, so the model, serial number, shaft and rotation must still match.

Will the SE521 or SE528 replace a Suzuki AP gearcase?

No. SEI’s current family listings state that these units do not replace AP models. If the engine model includes AP or uses Suzuki selective rotation, do not order from this collection without separate application confirmation.

Are these Suzuki lower units OEM or remanufactured?

No. The current SE521 and SE528 products are new aftermarket replacement gearcases manufactured by SEI Marine. They are not genuine Suzuki OEM assemblies and are not remanufactured units.

What warranty applies to these Suzuki lower units?

SEI publishes a three-year fault-free warranty for assembled outboard lower units, subject to its current written terms, exclusions and claim procedure. Review the warranty linked from the exact product page before purchase.

What are common signs of Suzuki lower-unit trouble?

Possible signs include lubricant leakage, milky or metallic gear lubricant, abnormal noise, shifting problems or loss of propeller drive. These symptoms do not identify the replacement unit by themselves, so have the existing gearcase diagnosed and record its identification details.

Should a replacement Suzuki lower unit be pressure tested or filled before installation?

Follow the installation, lubrication and leak-test procedure specified for the exact engine and replacement unit. Do not apply a universal pressure value or assume the unit ships filled; confirm included fluids and preparation requirements on the PDP or with the supplier before installation.

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