New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 0
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 1
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 2
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 3
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 0
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 1
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 2
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 3

New Aftermarket Yamaha 150-200HP 2-4-Stroke Counter-Rotation Outboard Lower Unit 90-418

$1,395.00
$1,550.00
$1,395.00
(-10%)

MPN : 90-418

SKU: SE90-418-A25
Availability: Out Of Stock
Product type: Lower Unit
Please hurry! Only 0 left in stock
Ratio/Motor/Length: 1.86:1 / 25" / 2 Stroke
Subtotal: $1,395.00
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 0

New Aftermarket Yamaha 150-200HP 2-4-Stroke Counter-Rotation Outboard Lower Unit 90-418

$1,550.00 $1,395.00
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 0
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 1
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 2
New Yamaha 150–200HP 2/4-Stroke (1990–2024) Replacement Lower Unit | Aftermarket | Counter Rotation | Fits 25″ Shaft | 3-Year Warranty image 3

New Aftermarket Yamaha 150-200HP 2-4-Stroke Counter-Rotation Outboard Lower Unit 90-418

$1,550.00 $1,395.00
Ratio/Motor/Length: 1.86:1 / 25" / 2 Stroke
Description
Description
x

Upgrade your Yamaha outboard with the SEI 90-418 Counter Rotation Lower Unit, built for 150HP–200HP 2-stroke and 4-stroke models (1990–2024).
This high-performance, direct-fit aftermarket replacement is ideal for twin-engine boats requiring left-hand (counter) rotation.
Fully assembled, pre-filled with premium gear lube, and backed by a 3-year warranty — ready to install out of the box.

Key Features

  • Designed for Yamaha 150–200HP 2-Stroke & 4-Stroke (1990–2024)

  • Counter Rotation (Left-Hand) — ideal for twin-engine setups

  • Fits 25″ shaft length configurations (offshore compatible)

  • Works with Yamaha V6 90° gearcases

  • Pre-filled with premium gear oil for hassle-free installation

  • Painted black — repaintable to match OEM finish

  • Direct-fit replacement — no modifications or adapters required

  • Built to OEM standards for durability and precision

  • 3-Year Manufacturer Warranty for complete peace of mind

Specifications

Feature Details
Model SEI 90-418
Rotation Counter (Left-Hand)
Compatible Horsepower 150HP – 200HP
Years Supported 1990 – 2024
Stroke Type 2-Stroke & 4-Stroke
Shaft Length 25″
Gear Ratio 1.86:1 or 2.00:1 (depending on engine)
Paint Black (Paintable Surface)
Replaces OEM Yamaha 150–200HP V6 Models
Warranty 3-Year
Condition New – Aftermarket
Installation Direct Fit – Pre-lubed & Ready to Install
Usage Offshore, Freshwater & Saltwater Compatible

Why Choose the Yamaha 150–200HP Counter Rotation Aftermarket Lower Unit?

Choosing a counter rotation lower unit is essential for boats using dual Yamaha engines — ensuring balanced thrust and improved steering control.
The SEI 90-418 delivers the same performance, strength, and longevity as OEM Yamaha gearcases at a more affordable price.

  • Optimized for Twin-Engine Rigs: Left-hand rotation balances torque with standard rotation engines.

  • OEM-Level Strength: Built with precision-machined gears and premium bearings.

  • Pre-Filled Convenience: Ships ready to install with premium-grade gear lube.

  • Perfect Fitment: Direct bolt-on replacement — no adjustments needed.

  • Trusted Reliability: Backed by SEI’s 3-year, no-fault replacement warranty.

 

Frequently Asked Questions – Yamaha 150–200HP Counter Rotation Replacement Lower Unit

1. Which Yamaha outboard models are compatible with the SEI 90-418 counter rotation lower unit?

The SEI 90-418 counter rotation lower unit is designed for Yamaha 150HP to 200HP 2-stroke and 4-stroke outboards manufactured from 1990 through 2024. It fits the Yamaha 90° V6 models with left-hand (counter) rotation, optimized for twin-engine setups requiring balanced thrust. This unit fits only 25″ shaft length configurations and provides a direct bolt-on replacement with no modifications necessary.

2. What gear ratios does this counter rotation lower unit offer, and how do I know which one to select?

The SEI 90-418 is available with gear ratios of either 1.86:1 or 2.00:1, depending on the specific Yamaha engine model. Owners should reference their outboard’s serial plate or official Yamaha documentation to match the gear ratio precisely, ensuring optimal propeller speed and engine performance on twin-engine vessels.

3. Is this SEI 90-418 lower unit new, rebuilt, or remanufactured?

This SEI 90-418 lower unit is a 100% new aftermarket assembly built to OEM specifications, not remanufactured or rebuilt. It ships fully assembled and pre-filled with premium marine gear lube, ready for immediate installation. No core return or deposit is required.

4. What warranty coverage does this counter rotation lower unit come with?

SEI Marine Products backs the 90-418 counter rotation lower unit with a 3-year fault-free manufacturer warranty. This warranty includes coverage against defects in materials and workmanship as well as mechanical failures during normal recreational use, providing significant peace of mind for boat owners.

5. What is the installation process, and does this unit require any preparation?

The SEI 90-418 unit comes painted black with a paintable OEM-style finish and is pre-filled with premium gear oil for hassle-free installation. It is a direct bolt-on replacement designed for the 25″ shaft Yamaha 150–200HP counter rotation models, requiring no adapters or special modifications. Simply align, bolt on, and your twin-engine setup will have balanced torque and control.

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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