Yamaha F150FET Lower Unit

Yamaha F150FET Lower Unit

Yamaha F150FET Lower Unit OEM 2019-2024 Yamaha

F150FET ,F150, F150A, F150B HP 20 and 25″ Outboard Lower Unit

 Overview & Information

The lower unit (also known as the gearcase) on a Yamaha F150FET is a critical component that houses the gears, driveshaft, propeller shaft, and water pump. It is responsible for transferring power from the engine to the propeller and for providing crucial cooling water to the engine.

Yamaha F150FET Lower Unit

Key Specifications for the Yamaha F150FET Lower Unit:

• Gear Ratio: 2.00:1 (This is the most common ratio for this model, meaning the propeller shaft turns once for every two turns of the crankshaft).
• Shift Type: Power Shift (Electro-hydraulic shifting, controlled by the Engine Control Unit (ECU) for smooth operation).
• Shaft Length: Available in different lengths (L, X, XX) to suit various boat transom heights.
  • L (Long): 20″
  • X (Extra-Long): 25″
  • XX (Extra-Extra-Long): 30″
• Displacement: The F150FET is a 2.7-liter, in-line 4-cylinder engine.
• Oil Capacity: Approximately 30 oz (approx. 0.89 liters) of specified Yamaha Gearcase Oil.

Yamaha F150FET Lower Unit

Common Parts & Components Inside the Lower Unit:

• Drive Shaft: Transfers power from the engine down into the gearcase.
• Propeller Shaft: Transfers power to the propeller.
• Forward & Reverse Gears: The gear set that changes the direction of thrust.
• Shift Mechanism: Includes a shift shaft, clutch dog, and in this model, hydraulic components for the Power Shift system.
• Water Pump Impeller: A crucial wear item that pumps water up to the engine for cooling. Should be replaced regularly (typically every 1-2 years).
• Propeller: The F150FET typically uses a 13-1/4″ to 15-1/2″ diameter propeller with varying pitches. Common sizes are in the 15″ to 17″ pitch range.
• Seals & Bearings: Keep water out and oil in, and allow the shafts to spin smoothly.

Common Issues & Maintenance Tips:

1. Water Intrusion: The most common sign of a problem is milky, creamy gear oil. This indicates that the seals have failed and water is mixing with the oil. This can lead to severe gear and bearing damage if not addressed immediately.
2. Impact Damage: Striking underwater objects can bend the propeller shaft, damage the gears, or crack the gearcase housing.
3. Worn Impeller: A failing water pump impeller will cause the engine to overheat due to lack of cooling water flow.
4. Corrosion: Especially in saltwater environments, the exterior and internal components can corrode.
5. Shifting Problems: Issues with the electro-hydraulic shift system can stem from the ECU, shift actuators, or internal hydraulic pressure problems.

Essential Maintenance:

• Gear Oil Change: Change the gearcase oil at least once a year, or every 100 hours of use. This is the best way to check for water intrusion.
• Water Pump Service: Replace the water pump impeller, housing, and seals every 1-2 years as preventative maintenance.
• Anode Inspection: Regularly inspect and replace sacrificial anodes to protect the lower unit from galvanic corrosion.
• Propeller Inspection: Check for nicks, dings, or bends that can cause vibration and damage the lower unit bearings.

Finding a Replacement or Parts:

If you need a replacement lower unit or parts, you will need your engine’s full model number and serial number. The F150FET was produced across several model years, and subtle changes can occur.

• Genuine Yamaha Parts: Use your serial number on the Yamaha Parts Catalog website or with a Yamaha dealer to find the exact parts.
• Aftermarket/SEI: SEI Marine manufactures reliable aftermarket replacement lower units that are a popular and cost-effective alternative to genuine Yamaha units. They often offer a 3-year warranty.

Always consult a qualified marine mechanic for diagnosis, repair, or replacement of the lower unit, as improper installation can lead to catastrophic failure.

1. New Lower Units

• Genuine Yamaha OEM (New): Typically comes with a 3-year limited warranty from Yamaha.

2. Used / Remanufactured Lower Units

• Remanufactured (Rebuilt): Warranty periods can vary significantly based on the rebuilder’s reputation and policy. A 1-year limited warranty is a common and respectable offering from a trusted machine