Yamaha - Lower Unit Assembly - Gearcase & Power Transfer - 64F-45300-20-4D

Overview

Lower units are one of those components you can’t ignore when they start acting up. I’ve seen motors lose that smooth feel or start making noise, and it almost always points down here. Swapping in a complete Yamaha assembly like this gets everything back to running tight and dependable. It’s the kind of fix that gives you confidence every time you shift into gear and head out.

Key Features

• Complete Gearcase Assembly – Includes internal gears and housing for a full lower unit replacement.
• Smooth Power Transfer – Delivers consistent engine output to the propeller.
• Corrosion-Resistant Construction – Built to handle saltwater exposure and harsh marine use.
• Reliable Gear Engagement – Provides clean shifting with reduced noise and vibration.

Engine & Boat Compatibility

Fits Yamaha outboard engines that utilize this style of lower unit assembly. Commonly used on mid-range horsepower outboards across fishing boats, bay boats, and recreational vessels.

FAQ

Q: What are the signs my lower unit needs replacement?
A: Grinding noise, slipping gears, water in the gear oil, or hard shifting are all common indicators.

Q: Can I continue running with a damaged lower unit?
A: It’s not recommended—damage can get worse quickly and lead to complete failure.

Q: Do I need to add gear oil before using this unit?
A: Yes, always check and fill to the correct level before running.

Q: How does saltwater affect lower units over time?
A: Salt can cause corrosion and wear, especially around seals, so regular flushing helps extend life.

Q: Is this part still current or has it been updated?
A: This assembly has been superseded by part number 64F-45300-20-8D, which is the latest version.