Yamaha F115LB 115HP – FourStroke 20-Inch Shaft

Yamaha F115LB 115HP FourStroke 20-Inch

The Yamaha F115LB 115HP FourStroke outboard motor utilizes a high-performance 1.8L DOHC architecture to deliver power and reliability for mid-sized coastal and inland vessels. Generating 115hp at 5500 RPM, this four-stroke powerhead offers an power-to-weight ratio with its 377 lbs dry weight. Its 20-inch shaft configuration makes it an ideal propulsion solution for center consoles, bay boats, and aluminum fishing hulls requiring efficient and responsive thrust. Operational efficiency is anchored by a sophisticated Multi-Point Electronic Fuel Injection system, which maintains peak volumetric efficiency across a broad 5000-6000 RPM range. Paired with a 2.15:1 gear ratio, the motor translates this combustion energy into low-end torque, allowing boaters to get on plane quickly even with heavy loads. This mechanical synergy provides the rugged reliability necessary for serious recreational fishing and long-distance maritime utility missions.

Technical Specifications of Yamaha F115LB

• Engine Type: 4-Cylinder DOHC 16-valve configuration designed for smooth power delivery.
• Displacement Output: 1.8L volume provides the necessary displacement for high-thrust marine operation.
• Horsepower Rating: 115hp at 5500 RPM delivers strong top-end speed and mid-range acceleration.
• Fuel Induction: Multi-Point Electronic Fuel Injection helps support precise combustion and easy starts.
• Alternator Capacity: 35 Amp output provides ample power for navigation electronics and lighting.
• Gear Ratio: 2.15:1 mechanical reduction allows for larger propeller pitches and high leverage.
• Shaft Length: 20-inch profile compatible with standard high-transom multi-species boats.
• Starting System: Electric ignition managed by a TCI Microcomputer helps support reliable start cycles.
• Trim System: Power trim and tilt allows for precision adjustment of the propeller thrust angle.
• Emissions Rating: C.A.R.B. 3-Star rating helps support compliance with strict environmental standards.

F-Series 115HP Propulsion

The F-Series propulsion dynamics are engineered to provide maximum thrust for mid-sized vessels without the excessive weight of older generations. By generating a true 115 horsepower at the propeller shaft, this engine helps support rapid acceleration and sustained top-end speed. The structural design of this series minimizes hydrodynamic drag, making it one of the most reliable marine propulsion units for boaters marine consistent power delivery.

EFI 4-Stroke System

The Multi-Point Electronic Fuel Injection (EFI) system precisely controls the fuel-to-air mixture entering the combustion chamber. This continuous calibration is designed to support that the four-stroke engine operates efficiently on standard 87-octane fuel, eliminating engine knock and optimizing fuel economy during long offshore runs. The EFI integration also helps support instant turnkey starting, regardless of ambient humidity or fluctuating maritime temperatures.

1.8L DOHC Technical

At the core of this engine is a 1.8-liter block featuring a Double Overhead Camshaft (DOHC) and 16 internal valves. This technical configuration dramatically improves engine breathing, allowing for faster intake of fresh air and rapid expulsion of exhaust gases. The result is a responsive powerhead that maintains thermal stability and mechanical smoothness across the entire 5000-6000 RPM wide-open throttle range.

F115LB 20 Inch Depth

The 20-inch shaft length is specifically calibrated for standard high-transom boat designs, ensuring the lower unit operates at the optimal aquatic depth. This dimension prevents the propeller from ventilating during sharp turns while keeping the water intakes submerged to maintain consistent engine cooling. Coupled with a 2.15:1 gear ratio, this shaft depth provides the appropriate mechanical leverage for lifting heavy fiberglass hulls onto a plane.

YDC-30 Aluminum Alloy

To combat the harsh reality of saltwater corrosion, the engine block and lower unit are cast using Yamaha’s proprietary YDC-30 aluminum alloy. This metallurgy significantly reduces copper content, preventing galvanic corrosion from eating away at critical internal and external components.Maintenance Tip: While the YDC-30 alloy is resilient, you must consistently flush the internal cooling jacket with fresh water after every saltwater excursion to prevent crystalline salt blockages.

Coastal Bay Boat Application

Weighing just 377 lbs, this motor is the definitive choice for coastal bay boats and shallow-draft center consoles. The balanced power-to-weight ratio helps support that the vessel’s stern doesn’t sit too low in the water, allowing anglers to navigate skinny coastal flats without bottoming out. Its quiet operation and minimal vibration mean fish are less likely to be spooked when maneuvering tightly around mangroves or nearshore reefs.

Yamaha 3-Year Protection

Investing in this outboard comes with the peace of mind provided by a comprehensive 3-year limited factory warranty. This protection plan covers manufacturing defects and helps support access to a vast, global network of certified marine technicians. Knowing that the electrical systems, powerhead, and lower unit are backed by high-pressure support allows operators to focus entirely on their maritime tasks rather than potential mechanical liabilities.