MerCruiser Alpha One Gen I complete standard-rotation sterndrive

Alpha OneĀ® Gen II Sterndrive Upper Applications

Shop Alpha One Gen II upper units for MerCruiser sterndrive applications, including SE116 replacement upper gearcases in 1.47, 1.62/2.00, 1.81 and 1.94/2.40 ratio options. Verify your existing drive ratio before ordering.

Alpha OneĀ® Gen II Sterndrive Upper Applications

Shop MerCruiser Alpha One Gen II upper gear cases (1991-present) ā€” replacement upper units for boaters whose lower gearcase is still in good condition and only the upper section needs replacing.

Pair this Alpha One Gen II upper unit with your existing lower gearcase for a targeted, cost-effective repair.

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  • Upper Gear Case | SE116 | 1.47 Ratio | Alpha One Gen II

    Upper Gear Case | SE116 | 1.47 Ratio | Alpha One Gen II SKU: SE90-116-01D
    MPN: 90-116-01D

    $965.00
    $1,071.15
    $965.00
    Restore the heart of your drive with this Premium Aftermarket Replacement for Mercruiser Alpha One Gen II units. Engineered with a 1.47 Gear Ratio, this upper gear housing delivers the high-torque performance and cooling efficiency required for V8 marine engines. Constructed with High-Strength Alloys...
    $965.00
    $1,071.15
    $965.00
  • Upper Gear Case | 90-116-01C | 1.62 or 2.0 Ratio | Gen II
    Out Of Stock

    Upper Gear Case | 90-116-01C | 1.62 or 2.0 Ratio | Gen II SKU: SE90-116-01C
    MPN: 90-116-01C

    $965.00
    $1,071.15
    $965.00
    Restore the dependable power of your drive system with this Premium Aftermarket Replacement for Mercruiser Alpha One Gen II upper gear housings. Engineered for mid-range torque, this unit is available in both 1.62 and 2.0 Gear Ratios to match your specific engine configuration. Built...
    $965.00
    $1,071.15
    $965.00
    Out Of Stock
  • Upper Gear Case | SE116 | 1.81 Ratio | Alpha One Gen II

    Upper Gear Case | SE116 | 1.81 Ratio | Alpha One Gen II SKU: SE90-116-01B
    MPN: 90-116-01B

    $965.00
    $1,071.15
    $965.00
    Restore peak propulsion efficiency to your drive system with this Premium Aftermarket Replacement for Mercruiser Alpha One Gen II upper gear housings. Engineered with a 1.81 Gear Ratio, this unit is precision-calibrated for mid-range torque delivery and High-Load Performance. Built with Heavy-Duty Internal Gears...
    $965.00
    $1,071.15
    $965.00
  • Upper Gear Case | 90-116-01A | 1.94 or 2.40 Ratio | Gen II

    Upper Gear Case | 90-116-01A | 1.94 or 2.40 Ratio | Gen II SKU: SE90-116-01A
    MPN: 90-116-01A

    $965.00
    $1,071.15
    $965.00
    Restore reliable power and smooth operation to your drive system with this Premium Aftermarket Replacement for Mercruiser Alpha One Gen II upper gear housings. Available in 1.94 and 2.40 Gear Ratios, this assembly is engineered to deliver high-torque mechanical advantage for smaller engine configurations....
    $965.00
    $1,071.15
    $965.00

A Clearer Way to Select Your Replacement Drive

Compare the configuration details that matter before choosing a sterndrive.

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Engineered for direct replacement

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Coverage on select lower units

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How to Choose the Correct Alpha One Gen II Upper Unit

The correct Alpha One Gen II upper unit should be selected from the existing sterndrive configurationā€”not from engine horsepower or visual appearance alone. Start by confirming that the drive is an Alpha One Gen II, then identify the current gear ratio and any available drive or upper-unit part numbers.

SE116 replacement upper gearcases are offered across several ratio paths, including 1.47, 1.62/2.00, 1.81 and 1.94/2.40. Because similar-looking drives can use different internal configurations, verify the ratio and identification information before purchasing a MerCruiser Alpha One Gen II replacement upper unit.

Verify These Details Before Ordering

  • Confirm the sterndrive is Alpha One Gen II
  • Identify the existing gear ratio
  • Record the engine or sterndrive serial number
  • Record any available upper-unit or drive part number
  • Check the current upper and lower drive configuration
  • Do not select the replacement only by horsepower
  • Do not assume two close gear ratios are interchangeable
  • Request fitment assistance if any identification is unclear

Alpha One Gen II Upper Unit Ratio Guide

Use this Alpha One Gen II gear ratio chart to compare the SE116 upper-unit options available for different ratio paths. Match your existing Alpha One Gen II upper unit ratio, drive identification and current configuration before ordering a replacement upper gearcase.

Gear Ratio SE116 Upper Unit / Ratio Reference
1.47 SE116 / 90-116-01D ā€” Related ratio reference: 1.50 / 1.47 path ā€” Confirm the existing drive ratio before ordering
1.62 / 2.00 SE116 / 90-116-01C ā€” Related ratio reference: 1.65 / 1.62 and applicable 2.00 path ā€” Verify the exact existing drive configuration
1.81 SE116 / 90-116-01B ā€” Related ratio reference: 1.84 / 1.81 path ā€” Match the existing drive identification and gear ratio
1.94 / 2.40 SE116 / 90-116-01A ā€” Related ratio reference: 1.98 / 1.94 and applicable 2.40 path ā€” Confirm the ratio and complete drive setup

Upper Unit, Lower Unit or Complete Alpha One Gen II Sterndrive?

Before ordering, identify which part of the sterndrive actually needs replacement. An Alpha One Gen II upper unit, lower unit and complete sterndrive are different assemblies and should not be treated as interchangeable shopping paths.

Upper Unit

  • Upper gearcase replacement
  • Ratio-specific SE116 upper-unit selection
  • Existing lower assembly being retained

Lower Unit

  • Lower gearcase replacement
  • Standard or counter-rotation lower-unit selection
  • Existing upper assembly being retained

Complete Sterndrive

  • Complete-drive replacement
  • Upper and lower assembly replacement together
  • Customers who do not need an individual upper-only solution
An informational comparison graphic titled 'STANDARD VS COUNTER ROTATION' showing two outboard motors and two propellers, with text explaining the difference in propeller direction when viewed from behind. The background is a real marina scene with water and boats, but the image functions as an explanatory diagram rather than a straightforward product photo.

Standard and Counter-Rotation Alpha One Gen II Applications

Standard and Counter-Rotation

Standard and counter-rotation describe the propeller and lower-drive configuration used in different Alpha One Gen II sterndrive applications. Rotation is especially important when identifying replacement lower units or complete drives, but it should not be used by itself to select an Alpha One Gen II upper unit.

When choosing an SE116 replacement upper gearcase, confirm the gear ratio, Alpha One Gen II drive identification and complete upper/lower configuration. Do not assume the correct upper unit solely from port or starboard drive position or from the direction of propeller rotation.

Shop Alpha One Gen II Upper Units by Gear Ratio

Choosing the correct Alpha One Gen II upper unit starts with the drive ratio. Use the options below to narrow the available SE116 replacement upper gearcases, then confirm your existing sterndrive identification before ordering.

  1. 1.47 Ratio Upper Unit

    Shop the Alpha One Gen II 1.47 upper unit option for applicable MerCruiser Gen II sterndrive configurations. Confirm the existing ratio and drive identification before replacement.

    View 1.47 Upper Unit

  2. 1.62 / 2.00 Ratio Upper Unit

    Explore the Alpha One Gen II 1.62 / 2.00 upper unit replacement path. Verify your current sterndrive ratio and application details before selecting this SE116 upper gearcase.

    View 1.62 / 2.00 Upper Unit

  3. 1.81 Ratio Upper Unit

    Shop the Alpha One Gen II 1.81 upper unit for applicable MerCruiser sterndrive configurations. Match the existing gear ratio and identification rather than ordering by engine size alone.

    View 1.81 Upper Unit

  4. 1.94 / 2.40 Ratio Upper Unit

    Browse the Alpha One Gen II 1.94 / 2.40 upper unit option for compatible SE116 replacement applications. Confirm the installed drive configuration before ordering.

    View 1.94 / 2.40 Upper Unit

When Do You Need an Alpha One Gen II Upper Unit?

An Alpha One Gen II upper unit replacement may be the correct shopping path when the service diagnosis or inspection points specifically to the upper gearcase assembly while the lower unit is being retained. Before purchasing, confirm which assembly actually requires replacement and verify the existing gear ratio.

If damage or wear affects other major sterndrive assemblies as well, compare the cost and fitment requirements of an upper-only replacement with an Alpha One Gen II lower unit or complete sterndrive. Correctly identifying the assembly first helps prevent ordering a part that does not match the repair.

What Customers Say

Perfect replacement lower unit for 1998 5.7L V8

Replaced a damaged lower gearcase on my 1998 Mercruiser 5.7L Alpha One Gen II. The product specs on Mariners Warehouse made verifying fitment foolproof. The unit bolted right up to my existing upper section, and having the internal water pump pre-installed made the job seamless.
Aaron Sterling Verified buyer
August 2026

Smooth gear engagement on 2002 4.3L V6

Ordered this Gen II lower application to replace a unit with worn forward gears. The shaft splines aligned perfectly with the upper driveshaft. Shifting into forward and reverse is crisp, and water pressure is back to factory levels.
Brandon Vance Verified buyer
July 2026

Clear serial number fitment guidance

The product description clearly highlighted the 1991-present Gen II specifications versus older Gen I drives. Confirming my engine serial range before ordering gave me complete confidence. Packed extremely well in heavy foam.
Caleb Montgomery Verified buyer
June 2026

Flawless fit for 2005 5.0L MPI bowrider

This standard rotation lower gearcase was a direct replacement for my damaged outdrive. All mounting studs lined up cleanly. Remember to install a fresh quad ring between the upper and lower housings during assembly.
Derek Reynolds Verified buyer
May 2026

Great replacement lower for 3.0L 4-cylinder

Replaced the lower housing on my 1996 runabout after hitting a submerged rock. The unit arrived fully assembled with the water pump impeller and fresh anodes. After the 10-hour break-in oil change, it operates completely noise-free.
Ethan Caldwell Verified buyer
April 2026

Solid build quality and fast dispatch

The lower drive was delivered safely in double-boxed packaging. Shafts were pre-greased and ready for mounting. It saved me thousands compared to an OEM Mercruiser dealer replacement.
Frank Harrison Verified buyer
March 2026

Reliable counter-rotation lower for twin setup

Purchased the LH counter-rotation lower unit configuration for our port engine. The propshaft tolerances and paint finish match factory quality. Customer support helped verify gear ratio compatibility before dispatch.
Garrett Hayes Verified buyer
February 2026

Exact match for 1994 Alpha Gen II drive

Finding specific Alpha One Gen II lower parts can be tricky, but this complete lower unit took all the guesswork out. High-volume water flow at idle and zero vibration across all RPM ranges.
Harvey Brooks Verified buyer
January 2026

Helpful Guides

Use these guides to identify your MerCruiser drive, understand gear-ratio selection and decide whether you need a complete sterndrive, upper unit or lower unit.

Alpha One Gen II gear ratio guide showing a replacement upper unit and 1.47, 1.62, 1.81, 1.94 and 2.40 ratio options

Alpha One Gen II Gear Ratio Guide: 1.47, 1.62, 1.81, 1.94 & 2.40

Alpha One Gen II Buying Guide Alpha One Gen II Gear Ratio Guide: 1.47, 1.62, 1.81, 1.94 & 2.40 Choosing...

Read More ā†’
Alpha One Gen II upper unit and lower unit separated to compare sterndrive replacement assemblies

Alpha One Gen II Upper vs Lower Unit: Which Assembly Do You Need?

MerCruiser Replacement Guide Alpha One Gen II Upper vs Lower Unit: Which Assembly Do You Need? An Alpha One Gen...

Read More ā†’
Mechanic identifying the correct Alpha One Gen II upper unit using drive labels, part numbers and gear ratio information

How to Identify the Correct Alpha One Gen II Upper Unit

SE116 Application Guide How to Identify the Correct Alpha One Gen II Upper Unit If you are asking, ā€œWhich Alpha...

Read More ā†’

Frequently Asked Questions

Which Alpha One Gen II upper unit fits my sterndrive?

The correct Alpha One Gen II upper unit depends on the existing drive configuration and gear ratio. Confirm that the sterndrive is Alpha One Gen II, identify the current ratio and record any available drive or upper-unit part numbers before selecting an SE116 replacement.

How do I identify my Alpha One Gen II gear ratio?

Start with the existing drive identification, serial information and any available ratio or part-number references. Because Alpha One Gen II gear ratio is a major selection factor for an upper unit, do not choose a replacement based only on horsepower or visual appearance.

What SE116 upper-unit ratios are available in this collection?

This SE116 upper unit collection is organized around 1.47, 1.62/2.00, 1.81 and 1.94/2.40 ratio options. The correct option still needs to be matched to the existing Alpha One Gen II drive configuration before ordering.

Can a 1.47 Alpha One Gen II upper replace a 1.50 ratio application?

Some replacement references use a 1.50-to-1.47 ratio path, but that does not mean every 1.50 application can automatically accept any 1.47 Alpha One Gen II upper unit . Verify the exact existing drive configuration and replacement reference before ordering.

What is the difference between 1.81 and 1.84 Alpha One Gen II ratios?

The 1.81 and 1.84 numbers can appear within related replacement and legacy ratio references, but they should not be treated as universally interchangeable. Match the existing Alpha One Gen II upper gearcase identification and complete drive configuration before selecting the replacement.

What does the 1.62 / 2.00 SE116 upper-unit option mean?

The 1.62 / 2.00 listing represents a specific SE116 replacement path used for applicable Alpha One Gen II configurations. Always verify which ratio and drive combination is installed on your boat before choosing the 90-116-01C upper unit .

Does counter rotation require a different Alpha One Gen II upper unit?

Counter rotation is particularly important when identifying lower-unit and complete-drive configurations, but rotation alone should not determine the upper unit. For an Alpha One Gen II upper unit replacement , verify the gear ratio and complete drive configuration as well.

What is the difference between the SE116 90-116-01A, 01B, 01C and 01D upper units?

The main shopping difference across these SE116 upper units is their ratio application path. The collection includes 90-116-01D for 1.47, 90-116-01C for 1.62/2.00, 90-116-01B for 1.81 and 90-116-01A for 1.94/2.40 ratio options.

Are Alpha One Gen I and Alpha One Gen II upper units interchangeable?

Do not assume Alpha One Gen I and Gen II upper units are interchangeable. Confirm the actual sterndrive generation and select a replacement specifically supported for the installed Alpha One Gen II configuration.

Should I replace the upper unit or the complete Alpha One Gen II sterndrive?

Choose an Alpha One Gen II upper unit when the repair requirement is limited to the upper drive assembly and the remaining sterndrive components are being retained. If both major drive assemblies require replacement, compare a complete Alpha One Gen II sterndrive instead.

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