Mercury Outboard Lower Unit Replacement – Fits 3.0L, 2.6L, 1.7L – 1.62 & 1.75 Ratio – Standard Rotation – SE221

Reliable Power Starts Below the Waterline

If your Mercury outboard is struggling with performance, noise, or gear failure, your lower unit may be the issue. The SE221 lower unit by SEI Marine is a high-quality replacement designed to restore smooth operation, power transfer, and confidence on the water.

Built for Performance & Longevity

Engineered to meet or exceed OEM specifications, this gearcase is compatible with select 3.0L V6, 2.6L Inline 6, and 1.7L Inline 4 Mercury engines. Whether you're cruising, fishing, or working, this unit delivers dependable performance under real-world marine conditions.

Perfect for Boat Owners Who Demand Reliability

Ideal for recreational boaters, fishing enthusiasts, and marine professionals who need a cost-effective, durable alternative to OEM lower units without sacrificing quality.

Why Choose SE221?

Unlike worn or rebuilt units, the SE221 is brand new, precision-built, and tested for reliability. It’s trusted by marine technicians and boat owners for its strength, smooth shifting, and long service life.

Key Features

• Heavy-duty construction for long-lasting durability

• Precision-engineered gears for smooth, quiet operation

• Available in 1.62 and 1.75 gear ratios

• متعدد shaft length options (20", 25", 30", Stub)

• Compatible with multiple Mercury engine configurations

• Corrosion-resistant finish for harsh marine environments

• Backed by SEI Marine quality assurance

Technical Specifications

Compatibility Notes

• Fits select Mercury engines including:

  • 3.0L V6 (2-Stroke) – 13 spline driveshaft

  • 2.6L Inline 6 (4-Stroke) – 20 spline driveshaft

  • 1.7L Inline 4 (4-Stroke) – 20 spline driveshaft

• Designed for engines within 135HP to 300HP range

• Always verify shaft length, spline count, and ratio before purchase

Variant Explanation

Choose the correct option based on your engine setup:

• 13/1.75/3.0L/20" Shaft → 3.0L V6, 2-stroke, 20-inch shaft

• 13/1.75/3.0L/25" Shaft → 3.0L V6, 25-inch shaft

• 13/1.75/3.0L/30" Shaft → 3.0L V6, 30-inch shaft

• 20/1.75/2.6L/20" Shaft → 2.6L inline 6, 4-stroke

• 20/1.85/2.6L/25" Shaft → Higher ratio for torque performance

• 20/2.08/1.7L/25" Shaft → Inline 4 setup for smaller engines

(Always match spline count + ratio + shaft length)

What’s Included

• Complete lower unit (gearcase assembly)

• Pre-installed internal gears

• Water pump housing (where applicable)

• Ready-to-install unit

Important Notes / Disclaimer

• Not compatible with all Mercury models—verify fitment before ordering

• Does NOT fit Verado V6/V8 engines

• Professional installation recommended

• Oil may need to be added before use

• Serial number verification is strongly advised