Yamaha LF115XB2 115HP 25″ Counter-Rotation Outboard

Description

The Yamaha LF115XB2 pairs 115HP with a 25-inch shaft, built with counter-rotation gearing for multi-engine offshore boats. The 1.8-liter inline-4 displaces 1832cc and weighs 386 lbs dry. Built for mid-transom configurations, the 25-inch shaft ensures ideal propeller depth and balanced tracking across heavy-duty fiberglass hulls navigating rough open ocean waters.

Running within a 5300-6300 RPM range, this offshore engine sustains cruising speeds across long tournament distances. The 2.15:1 gear ratio converts combustion force into a flat torque curve, so heavy boats get on plane without burying the stern under load. This Japan-built platform is engineered to reduce hull vibration during long-range deep-sea operations.

Technical Specifications of Yamaha LF115XB2

• Electronic fuel injection uses a multi-point sequential track for strong thermal efficiency across all cylinders.
• A 35-Amp gross alternator generates enough power to keep house battery banks topped off.
• Remote mechanical control gives responsive vessel tracking adjustments.
• Power trim and tilt simplifies trailering and shallow-water operation by moving the lower unit clear.
• A 3.2-liter oil sump supports continuous lubrication during hard wide-open-throttle runs.
• The counter-rotation gearcase balances propeller torque to maintain tracking on multi-engine express cruisers.

DOHC In-Line Four Architecture

The 16-valve DOHC design treats the cylinder layout of this inline-4 block to optimize thermal efficiency, shaving response lag off the powerhead while improving volumetric efficiency under load.

Sequential Track Fuel Induction

Electronic fuel injection sprays gasoline into the intake tracks for clean combustion on 87-octane fuel, giving immediate throttle response and reliable cold starts.

Hydrodynamic Gear Housing Profile

Oversized internal gears and a 2.15:1 gear ratio profile minimize underwater drag at high cruising speed, mitigating gear chatter and ensuring smooth power transmission.

Mechanical Remote Helm Layout

Digital electronic control integrates with the steering setup to automate multi-engine tracking and trim adjustments, letting captains execute precise docking maneuvers.

Opposing Twin Engine Configuration

Twin-engine configurations for mid-size offshore hulls, multi-engine coastal center consoles, and deep-V bay boats in the 20-28 ft range are the target. The mid-length shaft delivers strong leverage and vibration dampening driving through steep waves.

Cowling Access And Lubrication

A multi-piece outer cowling gives fast access to critical checking points, cutting service time down. The drain plug keeps oil changes clean. Pro Tip from the Shop: pull the gear lube plugs at the dock and use a lower unit pump to push fresh oil from the bottom up, keeping air pockets out of the gear housing.