Yamaha F115JB 115HP – Jet Drive FourStroke 20-Inch

Yamaha F115JB 115HP Jet Drive 20-Inch

The Yamaha F115JB 115HP Jet Drive outboard motor utilizes a high-performance 4-Cylinder DOHC architecture to deliver specialized shallow-water propulsion. With an 1832 cc displacement, this four-stroke powerhead generates 115hp at the crankshaft, resulting in a potent 80hp at the jet pump. Its 378 lbs dry weight and 20-inch shaft configuration make it an ideal choice among reliable marine propulsion systems for aluminum river boats and technical skiffs requiring extreme shallow-water capability.

Operational efficiency is anchored by a sophisticated Electronic Fuel Injection (EFI) system, which maintains peak volumetric efficiency across a broad 5300-6300 RPM range. The jet drive configuration eliminates the lower unit torpedo and propeller, allowing boaters to traverse rocky riverbeds and sandbars that would disable a traditional prop-driven motor. This mechanical synergy provides the rugged reliability necessary for serious riverine exploration and utility missions.

Technical Specifications of Yamaha F115JB

• Engine Type: 4-Cylinder DOHC (Jet Drive) configuration designed for smooth power delivery.
• Displacement Output: 1832 cc volume provides the necessary displacement for high-thrust jet flow.
• Horsepower Rating: 115hp at the crank delivers 80hp of effective jet propulsion at the nozzle.
• Fuel Induction: Electronic Fuel Injection (EFI) ensures precise combustion and easy starts.
• Alternator Capacity: 35 Amp output provides ample power for navigation electronics and lighting.
• Gear Ratio: 1.00:1 direct jet drive synchronization allows for immediate throttle response.
• Shaft Length: 20-inch profile compatible with standard high-transom river boats and skiffs.
• Starting System: Electric start managed by a TCI Micro-Computer ensures reliable ignition cycles.
• Trim System: Power trim and tilt allows for precision adjustment of the jet nozzle angle.
• Emissions Rating: C.A.R.B. 3-Star rating ensures compliance with strict environmental standards.

F-Series 115HP Propulsion

The F-Series architecture maximizes air intake and exhaust efficiency to sustain high-RPM operations in demanding marine environments. This 115HP platform delivers 80HP directly at the jet nozzle, ensuring that the vessel has the raw thrust required to plane quickly against river currents. The inline four-cylinder configuration minimizes internal vibration, preserving the structural integrity of the transom during aggressive riverine navigation.

EFI 4-Stroke System

An onboard micro-computer monitors throttle position and atmospheric pressure to adjust the fuel-to-air ratio instantly. This EFI system ensures that the powerhead remains highly responsive while running on standard 87 octane fuel, providing significant savings on long-distance utility trips. Optimized fuel atomization prevents carbon buildup within the 10.0:1 compression cylinders, extending the service life of internal rotating components.

4-Cylinder DOHC Technical

Utilizing double overhead cams and four valves per cylinder, this advanced 1832 cc block is designed to maintain thermal stability. The TCI micro-computer calculates spark timing to the millisecond, ensuring that the engine fires instantly in freezing or tropical environments. Furthermore, the 35-amp alternator maintains battery charge while running navigation lights and sonar equipment, which is essential for remote expeditions.

F115JB 20 Inch Depth

Utilizing a direct-drive 1.00:1 gear ratio, this specialized 20-inch profile maximizes water velocity through the internal impeller. The through-jet exhaust configuration reduces hydrodynamic drag, allowing the jet output to provide immediate hole-shot performance even when heavily loaded. This engineering allows operators to safely navigate white water and rocky shoals without traditional lower unit impact concerns.

YDC-30 Aluminum Alloy

The engine block and critical lower components are cast from Yamaha’s proprietary YDC-30 aluminum alloy, providing an exceptional barrier against corrosive aquatic environments. The lubrication system utilizes a wet sump architecture to ensure constant oil flow, reducing internal friction during sustained high-speed transit. Maintenance Tip: Always flush the jet pump and cooling jacket with fresh water after operating in muddy or salty environments to prevent abrasive mineral deposits.

Technical River Skiff Application

Allowing the operator to fine-tune the jet’s exit angle at the nozzle seamlessly compensates for variable weight distribution. This power trim functionality is vital for technical river skiffs and shallow-draft center consoles requiring a professional remote helm interface. By dynamically adjusting the trim, the vessel can maintain its plane in choppy currents, improving both fuel economy and maneuvering characteristics.

Yamaha 3-Year Protection

The 378 lbs lightweight design significantly reduces transom stress while providing class-leading structural strength for rough water conditions. Investing in this jet-drive platform ensures access to a global service network and genuine parts support for years of trouble-free operation. This factory warranty guarantees peace of mind, protecting the high-performance components that make riverine exploration and shallow-water navigation possible.