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Replace or upgrade your Yamaha outboard with this premium aftermarket counter-rotation lower unit designed for Yamaha 200HP, 225HP, and select 250HP V6 models (1990–2019).
Engineered for precision and durability, the SEI 90-428 lower unit fits both 2-stroke and 4-stroke Yamaha V6 engines and installs directly—no modifications required. Whether you run offshore or freshwater, this lower unit ensures smooth operation, long gear life, and dependable reverse performance.
It’s available in 25″ and 30″ shaft lengths with 1.81:1 (2-stroke) or 2.0:1 (4-stroke) gear ratios, built to OEM specs and backed by a 3-year, fault-free warranty for total peace of mind.
Key Highlights
Counter Rotation — perfect for twin-engine setups
Compatible with Yamaha V6 200-250HP outboards (1990–2019)
Direct-fit installation – no adjustments or modifications
Heavy-duty construction for saltwater and freshwater
Painted black (can be repainted to match your engine)
Long-lasting performance backed by a 3-year warranty
| Feature | Details |
|---|---|
| Product Name | Yamaha V6 200–250HP Counter Rotation Lower Unit |
| Compatible Models | 2-Stroke & 4-Stroke V6 |
| Horsepower Range | 200HP / 225HP / Some 250HP |
| Years Supported | 1990–2019 |
| Rotation | Counter Rotation Only |
| Shaft Length | 25″ / 30″ |
| Gear Ratios | 1.81:1 (2-Stroke) / 2.0:1 (4-Stroke) |
| Condition | New – Aftermarket |
| Paint Finish | Black (Paintable to Match) |
| Warranty | 3 Years |
| Part Code / SKU | 90-428 |
| Installation | Direct Fit – No Modifications Required |
| Usage | Freshwater & Saltwater Compatible |
Choosing the aftermarket Yamaha 200–250HP counter-rotation lower unit gives you OEM-level performance without the high price tag. It’s designed for long-term reliability, easy installation, and precise handling in twin-engine setups. With its 3-year warranty and strong build quality, it’s a smart investment for any serious boater or marine mechanic.
The SEI 90-428 fits most Yamaha 200HP and 225HP V6 2-stroke and 4-stroke outboards as well as select 250HP 76° V6 models manufactured between 1990 and 2019. It is designed specifically for counter rotation applications ideal for twin-engine boats.
This unit is available in 25″ and 30″ shaft lengths. Gear ratios offered are 1.81:1 for 2-stroke engines and 2.0:1 for 4-stroke engines, matching OEM specifications for optimal performance and durability.
The SEI 90-428 is a brand-new aftermarket lower unit built to precise OEM standards. It offers fully assembled components with a heavy-duty design for both freshwater and saltwater use, backed by a 3-year fault-free warranty.
Installation is a direct bolt-on fit that requires no modifications or adapters. It is designed for hassle-free replacement with the same exact fitment as original Yamaha counter-rotation models.
SEI provides a comprehensive 3-year fault-free warranty covering defects in manufacturing and mechanical failures under normal recreational use, giving you confidence in the unit’s long-term reliability.
Looking for other models or gear ratios?
Browse all Yamaha Lower Units here — find compatible options for 40HP, 60HP, 115HP, 150HP, and more Yamaha outboards.
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