Description

The Yamaha 40hp 2-stroke outboard motor is highly regarded for its high power-to-weight ratio, simple mechanical design, and brisk acceleration compared to modern four-stroke alternatives. While production largely shifted to four-strokes after the early 2000s, these engines remain popular in used markets and for commercial use in specific regions.

Technical Specifications

Yamaha produced both 2-cylinder (Enduro series) and 3-cylinder configurations of this motor.

Engine Type: In-line 2 or 3-cylinder, depending on the specific model (e.g., E40X is a 2-cylinder, while the 40V is a 3-cylinder).

Displacement: Typically 698cc to 703cc.

Dry Weight: Ranges from approximately 125 lbs (57 kg) to 145 lbs (66 kg) for vintage models, significantly lighter than the ~214 lbs of modern four-strokes.

Fuel System: Carbureted; requires 50:1 pre-mixed fuel and oil or uses an autolube injection system on certain models.

Starting Method: Manual recoil (rope) pull start or optional electric start.

Performance and Efficiency

Acceleration: 2-stroke designs produce power on every revolution, providing immediate throttle response ideal for getting small boats (14–18 feet) onto plane quickly.

Fuel Consumption: Averages between 3.5 and 5 gallons per hour at cruising speeds, though it can rise to 6–7 GPH at wide-open throttle.

Top Speeds: Users report speeds between 28–35 mph on typical aluminum fishing boats, depending on load and hull design.

Notable Models

Yamaha 40V: A refined 3-cylinder model praised by reviewers at TradeABoat for its mechanical balance, reduced vibration, and smoother power delivery compared to 2-cylinder versions.

Yamaha E40 Enduro: Part of a series developed for commercial use in harsh conditions, featuring enhanced durability in the crankshaft and cylinder block.

Yamaha 40X: A common 2-cylinder workhorse known for its simplicity and ease of field repair

Maintenance: Requires regular spark plug checks, carburetor cleaning, and annual water pump impeller replacement.

Parts Availability: Despite being out of production in many regions, OEM and aftermarket parts remain widely available through marine suppliers like RJ Nautic

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