Honda Marine BF40/BF50 EFI - General Overview


Honda engineers strive for product excellence and continuous improvement - providing new and innovative features to improve Honda products. When the team at Honda Marine recognized a need for programmed electronic fuel injected (PGM-FI) outboards in the mid-horsepower range, the process began to redesign the group's 40 and 50 horsepower (hp) models. Honda engineers also noted boaters' need for outstanding acceleration and exceptional fuel economy. The redesigned BF40 and BF50 EFI deliver on both.


The new BF40 and BF50 EFI offer a full complement of technologies geared towards performance and fuel economy. Their high-performance gear case and 2.08:1 gear ratio, coupled with Honda's revolutionary Boosted Low Speed Torque (BLAST) system, create a strong holeshot and competitive top-end speed.


New to the BF40/50 is a Multi-Port Electronic Fuel Injection (EFI) fuel delivery system. Mated to a dynamic engine control module (ECM), EFI delivers easy starting and top fuel economy in a lightweight package.


Utilizing an oxygen (O2) sensor in the exhaust manifold, Honda's exclusive Lean Burn Control system automatically adjusts the air/fuel mix according to speed and load, delivering unsurpassed efficiency and a fuel savings of nearly 20 percent in "cruise mode" from 2500 to 4000 rpm. The engines also realize exceptional fuel efficiency at low rpm, and operate as low as 800 rpm for slow trolling.


The engines' best-in-class 22-amp alternator (17 amps charging), ignition, and other critical components are mounted near the top of the powerhead to ensure that all are kept cool and dry. By extension, a camshaft-driven, automotive-style oil pump contributes to the long-term durability of critical engine components.

In addition to Honda's exclusive, double-sealed and multi-layered Four-Front Corrosion Protection (paint) System, the BF40 and BF50 EFI offer several other features designed to prevent damage caused by the harsh marine environment. A unique one-touch anode check system and improved waterproofing inside the engine cover and gear case are just a few of the innovative features Honda has added to promote the motors' long-term durability.

Ease of Maintenance

In addition to improved fuel efficiency and performance characteristics, the BF40 and BF50 EFI also incorporate a number of features designed to facilitate maintenance. An automotive-type oil filter and color-coded oil fill and dipstick simplify fluid level checks and changes. Additionally, both are compatible with Honda's HDS portable diagnostic system to facilitate on-water service.

Best-In-Class Features

  • Lightest weight in class
  • Best-in-class holeshot and top-end performance
  • Best-in-class fuel economy
  • High-performance gear case with low 2.08:1 gear ratio
  • Superior battery charging capacity (17 amps)
  • New adjustable-angle tiller handle
  • Low operational cost
  • Complies with 2008 CARB 3-Star emissions regulations
  • True 5-year, factory-backed, non-declining limited warranty

Honda-Exclusive Technologies

  • Boosted Low Speed Torque (BLAST) system
  • Lean Burn Control with oxygen (O2) sensor
  • High-performance gear case design
  • 22-amp alternator
  • Best-in-class battery charging capacity (17 Amps)
  • Patented 4-Front Corrosion Protection System
  • Non-linear mounting system

Ease Of Use

  • Multi-Port Programmed Fuel Injection (PGM-FI)
  • Multiple cowl latch points for watertight seal and superior protection
  • Color-coded oil fill and dipstick
  • Trolls to 800 rpm
  • Easy-adjust rocker arms; no multiple shims or trial-and-error adjustments
  • Stainless steel components
  • Engine alert system
  • 3-step angle adjustable tiller handle (7°, 13°, 21°)
  • Top-mounted oil fill
  • Automotive-type oil filter
  • Engine command system
Honda Marine BF40/50 EFI Glossary Of Terms
22-amp Alternator (17 amps charging) Keeps battery banks charged all day, even when running multiple accessories.
4-Front Corrosion Protection A patented double-sealed, multi-layer paint process fights off corrosion from harsh marine environments. The base is a Honda aluminum alloy, followed by a double-sealed treatment, an epoxy primer undercoat, and an acrylic resin metallic coating, finished with a clear overcoat of acrylic for UV protection.
4-Lamp Warning System Tiller models feature a new 4-lamp warning system built directly into the tiller handle, while remote control models deliver alerts via messaging through Honda's multi-function digital gauges or a special indicator built into the unit's control box.
Boosted Low Speed Torque (BLAST) Advances ignition timing during "hammer-down" acceleration, resulting in explosive holeshots.
Engine Alert System Monitors vital engine functions and alerts the operator - with a light, buzzer, and/or rpm reduction - of any problems.
Engine Command System Constantly accepts input from multiple sensors. The system delivers instant starts, smooth operation, strong performance, and excellent fuel efficiency.
High-Performance Gear Case Design The BF40/50 EFI's redesigned gear case features an enlarged bullet and new drag-reducing anti-splash and anti-ventilation plates.
Lean Burn Control Utilizes an oxygen (O2) sensor along with the Engine Command System to automatically adjust the air/fuel mix according to speed and load, providing 20 percent greater fuel economy in "cruise mode" from 2500 to 4000 rpm.
Mikuni® Long Tube Intake Track System Long intake runners combine with patented BLAST system to provide exceptional low-end torque and strong holeshots
Multiple Cowl Latch Points Easy-to-open front and back latches ensure a water-tight seal for superior protection.
Multi-Port Programmed Fuel Injection (PGM-FI) Delivers precise amounts of air/fuel to each cylinder, resulting in quick starts, instant throttle response, and low fuel consumption. PGM-FI employs microprocessor technology to accurately control ignition timing during start-up and across the entire rpm range, providing optimal overall operation.
Patented, Non-Linear Rubber Mounts Provide smoother operation at all engine speeds.
Single Overhead Camshaft (SOHC), In-Line 3-Cylinder Design Uses a single overhead cam to deliver an optimal air/fuel mixture for maximum torque and combustion efficiency.
Top-Mounted Electronics The alternator, ignition, and other critical components are mounted near the top of the powerhead to ensure all are kept cool and dry.
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