Product Overview
This 2004 Yamaha 150 HP 4-Stroke outboard lower unit gear case is a used replacement assembly designed for compatible Yamaha 150 HP outboard applications requiring a 25″ XL shaft configuration. The unit engages gears properly and has been pressure tested at 12 PSI, where it successfully held pressure.
The lower unit has an excellent-condition skeg, while the cavitation plate is damaged. Gear oil inspection found no metal contamination, although water was present in the drained gear oil. Buyers should carefully review the photos and confirm compatibility and condition before installation.
Technical Specifications
| Specification | Details |
|---|---|
| Brand | Yamaha |
| Model Year | 2004 |
| Horsepower | 150 HP |
| Engine Type | 4-Stroke |
| Part Type | Lower Unit / Gear Case |
| Shaft Length | 25″ XL |
| Rotation | Standard Right-Hand Rotation |
| Gear Engagement | Gears Engage Properly |
| Pressure Test | Passed — Held 12 PSI |
| Gear Oil — Metal Found | No |
| Gear Oil — Water Found | Yes |
| Skeg Condition | Excellent |
| Cavitation Plate | Damaged |
| Condition | Used |
Complete Installation-Ready Package
This listing includes the Yamaha lower unit / gear case assembly as shown and is intended as a replacement lower-unit assembly for a compatible Yamaha 150 HP 4-Stroke outboard.
- Yamaha lower unit / gear case
- 25″ XL shaft configuration
- Standard right-hand rotation
- Internal gearing and gear engagement assembly
- Skeg
- Propeller shaft and associated lower-unit components
- Installation-related components present on the listed assembly
Final compatibility should be confirmed against the engine model, shaft length, rotation, mounting configuration, and application before installation.
Condition & Performance
This is a used lower unit with several important condition points documented.
- Gears engage properly.
- Pressure tested at 12 PSI and held pressure.
- No metal was found in the drained gear oil.
- Water was found in the drained gear oil.
- Skeg is reported to be in excellent condition.
- Cavitation plate is damaged.
- Please review all product photos carefully for the actual physical condition.
Why Choose This Yamaha Lower Unit?
A properly matched replacement lower unit can provide a practical solution when an existing gear case has sustained damage or requires replacement. This Yamaha assembly has already been checked for gear engagement and pressure retention, providing useful condition information before installation.
Installation Considerations
- Confirm compatibility with your Yamaha 150 HP 4-Stroke application.
- Verify the required 25″ XL shaft configuration.
- Confirm right-hand rotation requirements.
- Inspect seals, bearings, shafts, and other components before installation.
- Because water was found in the gear oil, the lower unit should be thoroughly inspected and serviced before being placed into regular operation.
- The damaged cavitation plate should be evaluated before installation.
- Verify propeller and related hardware compatibility with your specific application.
Important Product Information
Brand: Yamaha
Model Year: 2004
Horsepower: 150 HP
Engine Type: 4-Stroke
Part Type: Lower Unit / Gear Case
Shaft Length: 25″ XL
Rotation: Standard Right-Hand
Gear Engagement: Proper
Pressure Test: Held 12 PSI
Gear Oil: No metal found; water found
Skeg: Excellent condition
Cavitation Plate: Damaged
Condition: Used
Streamline Mobile Marine
At Streamline Mobile Marine, we focus on providing dependable marine power solutions backed by professional guidance and practical installation support.
Whether you’re replacing a damaged lower unit, restoring an existing outboard, or completing a marine repair, our team can help you identify the right component and installation configuration for your application.
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