SE405 Lower Unit – Fits Yamaha V4 115-130 HP 2-Stroke (Replaces 6E5-45300-27-8D)

Product Details

This is a complete aftermarket SE405 Lower Unit designed to fit Yamaha V4 115-130 HP 2-Stroke outboard motors manufactured between 1984 and 2005. It features a 2.0:1 gear ratio, a 25" shaft, and standard right-hand rotation, making it a reliable replacement for your worn or damaged gearcase.

It serves as a direct interchange for SEI Marine part number 90-405-A25 and Yamaha OEM part numbers 6E5-45300-27-8D, 6E5-45300-2A-8D, and 6E5-45300-28-8D.

• Direct bolt-on installation for a perfect fit.
• Arrives fully assembled with water pump, gears, driveshaft, and shift shaft.
• Covered by an industry-leading 3-year no-fault warranty.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Technical Specs

Product Type

Complete Lower Unit

Installation

Direct Bolt-On Replacement

Gear Ratio

2.0:1

Rotation

Right-Hand (Standard)

Shaft Length

25" (635 mm)

Housing Material

Marine-Grade Aluminum

Housing Color

Black (Paintable)

Dimensions

69.0 cm x 22.5 cm x 123.5 cm (L x W x H)

Warranty

3-Year No-Fault Warranty

Cooling System

Water-Cooled

Cooling Water Pickup

Side Intake

Included Components

Fully assembled with water pump, gears, driveshaft, and shift shaft

What’s in the Box

• One complete lower unit assembly

Installation Notes

1. Disconnect the engine's battery before beginning work.
2. Place a drain pan under the gearcase and remove the drain and vent plugs to empty the old gear lube.
3. Disconnect the shift linkage connecting the engine to the lower unit.
4. Remove the mounting bolts that secure the lower unit to the engine's midsection.
5. Carefully lower and remove the old unit. Be aware it can be heavy.
6. Clean the mating surfaces of any old gasket material or corrosion.
7. Align the driveshaft, water tube, and shift shaft, then carefully guide the new unit into place.
8. Reinstall the mounting bolts, tightening them to the torque specified in your service manual.
9. Reconnect the shift linkage and test for proper engagement in forward, neutral, and reverse.
10. Refill the gearcase with fresh, high-quality marine gear lubricant according to manufacturer recommendations.

Troubleshooting & FAQ

Safety & Important Info

• Verify images and specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or quality control.