Yamaha 40VEO Specifications
| Engine Model: Yamaha 40VEO |
| Engine Type: 2-stroke inline 3-cylinder gasoline outboard engine |
| Total Displacement: 42.6 cu.in (698 cc) |
| Rated Engine Power: 40 Hp (29.4 kW) at 5000 rpm |
| Fuel System: Carburetor |
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The Yamaha 40VEO is a 40-horsepower,
three-cylinder, two-stroke outboard motor that represents a significant
engineering achievement from Yamaha's extensive experience in two-stroke
design. This engine is built around a popular three-cylinder
configuration featuring loop-charged fuel induction, which delivers
substantial power along with smooth and responsive operation throughout
the entire RPM range.
The 40VEO is specifically designed as an electric start model with
remote control operation, making it an ideal choice for boaters seeking
reliable, straightforward power for a variety of applications including
fishing, recreational boating, and commercial use.
Notable features include an automatic oil injection system that
eliminates the need for pre-mixing fuel, a Prime Start enrichment system
for effortless cold starts, and a built-in charging system that
continuously replenishes the battery. All components are constructed
from high-strength materials with multi-layer paint finishes for
enhanced corrosion resistance.
Engine type: 2-stroke, L (inline 3-cylinder).
Number of cylinders: 3.
Total displacement: 698 cc (42.6 cu in).
Bore and stroke: 67.0 x 66.0 mm (2.64 x 2.60 in).
Compression ratio: 6.0:1.
Maximum output: 29.4 kW (40 hp) at 5,000 rpm.
Full throttle operating range: 4,500-5,500 rpm.
Fuel system: 3 carburetors.
Intake system: Reed valve.
Scavenging system: Loop charge.
Ignition system: CDI (Capacitor Discharge Ignition).
Starting system: Electric.
Control system: Remote control.
Alternator output: 12V, 6A (80W).
Enrichment system: Prime Start (automatic).
Advance type: Electric automatic.
Spark plug: NGK B7HS-10 or NGK BR7HS-10.
Spark plug gap: 0.9-1.0 mm (0.035-0.039 in).
Cooling system: Water, thermostatically controlled.
Exhaust system: Through propeller boss.
Lubrication system: Automatic oil injection.
Recommended fuel: Regular unleaded gasoline, minimum 86 octane.
Recommended oil: 2-stroke outboard motor oil, NMMA-certified TC-W3.
Engine oil tank capacity: 1.5 L (1.6 US qt).
Gear oil type: Hypoid gear oil SAE90.
Gear oil capacity: 0.43 L (0.45 US qt).
Gear ratio: 1.85 (24/13).
Gear shift positions: Forward - Neutral - Reverse.
Reduction gear type: Spiral bevel gear.
Clutch type: Dog clutch.
Propeller shaft type: Spline.
Propeller direction (rear view): Clockwise.
Trim system: Manual tilt.
Tilt angle positions: 8, 12, 16, 20, 24 degrees.
Tilt-up angle: 66 degrees.
Steering angle: 40 + 40 degrees.
The Yamaha 40VEO features a robust three-cylinder powerhead designed for
durability and smooth power delivery. The cylinder block houses three
precision-machined cylinders with a bore of 67.0 mm and stroke of 66.0
mm, resulting in the total displacement of 698 cc. The powerhead
utilizes a loop-charge scavenging system, which creates a swirling
motion of the air-fuel mixture within the cylinders for more complete
combustion and efficient exhaust gas removal.
The crankshaft is supported by high-quality bearings and is balanced to
minimize vibration during operation. The intake system employs reed
valves, which act as one-way check valves to optimize air-fuel flow into
the crankcase and prevent backflow, enhancing low-end torque and
throttle response.
The cylinder head is designed to provide optimal combustion chamber
shape for efficient burning of the air-fuel mixture. The engine features
a compression ratio of 6.0:1, which is appropriate for the two-stroke
design and allows for reliable operation on regular-grade fuels.
The Yamaha 40VEO employs a sophisticated fuel system utilizing three
separate carburetors, one for each cylinder, ensuring precise fuel
delivery and balanced performance across all cylinders. This
multi-carburetor setup contributes to the engine's smooth operation and
responsive acceleration throughout the RPM range.
The fuel system draws fuel from an external 24-liter fuel tank, which is
included with the engine. A key feature of the 40VEO is the Prime Start
enrichment system, which automatically provides the correct fuel mixture
for cold starts without requiring the operator to manually operate a
choke.
This system simplifies starting procedures and ensures reliable ignition
in various weather conditions. The fuel system includes a replaceable
fuel filter that should be checked periodically for water or foreign
matter. Regular inspection of fuel lines for leaks, cracks, or
malfunctions is essential for safe operation.
The Yamaha 40VEO features an advanced automatic oil injection system,
which represents a significant convenience over traditional pre-mix
two-stroke engines. This system continuously monitors engine load and
RPM, precisely metering the exact amount of oil required for proper
lubrication under all operating conditions.
The oil is drawn from a dedicated 1.5-liter (1.6 US quart) onboard oil
tank, eliminating the need for the operator to pre-mix oil with fuel in
the main gasoline tank. The recommended oil is NMMA-certified TC-W3
two-stroke outboard motor oil, with Yamalube 2 being the preferred
choice.
The system includes an oil level indicator and an alarm system that
alerts the operator to low oil conditions or lubrication system
malfunctions, protecting the engine from potential damage. The oil
injection system provides optimal lubrication across all engine speeds
while reducing smoke and carbon buildup compared to fixed-ratio pre-mix
operation.
The cooling system is a raw-water, thermostatically controlled design
that draws water from the surrounding environment to regulate engine
temperature. A water pump, driven by the driveshaft, pulls water through
an inlet in the lower unit and circulates it through water jackets
surrounding the cylinders and cylinder head.
The thermostat regulates coolant flow, allowing the engine to reach
optimal operating temperature quickly and maintaining consistent
temperatures during operation. The system includes an overheat alarm
that alerts the operator if cooling water flow is insufficient or if the
engine exceeds safe operating temperatures.
Regular maintenance includes flushing the cooling system with fresh
water after operation in salt, brackish, or polluted water to prevent
deposit buildup and corrosion. The water pump impeller should be
replaced at recommended intervals to ensure proper cooling system
function.
| Mid Section and Lower Unit |
The mid section connects the powerhead to the lower unit and houses the
exhaust tube and driveshaft. The lower unit contains the reduction
gearing and propulsion components engineered for efficiency and
durability. The gear ratio is 1.85:1 (24/13), providing an optimal
balance of acceleration and top-end performance. The reduction gears are
of the spiral bevel type, selected for their strength, smooth operation,
and ability to handle the torque produced by the three-cylinder engine.
The clutch mechanism is a dog clutch design that provides positive
engagement for shifting between forward, neutral, and reverse gears. The
propeller shaft utilizes a spline drive system for secure propeller
attachment and efficient power transfer.
The gear housing is filled with hypoid gear oil meeting SAE90
specifications, with a total capacity of 0.43 L (0.45 US qt). Regular
inspection and periodic changing of the gear oil is essential to detect
water ingress or metal particles that may indicate internal wear. The
lower unit incorporates sacrificial anodes to protect against galvanic
corrosion in saltwater environments.
The Yamaha 40VEO is equipped with a manual tilt system that allows the
operator to adjust the engine angle for optimal performance and shallow
water operation. The system provides five distinct trim angle positions:
8, 12, 16, 20, and 24 degrees, allowing fine-tuning of boat attitude for
various loading conditions and water surfaces.
Proper trim adjustment affects boat performance significantly; trimming
the engine in helps achieve planing and improves handling in rough
water, while trimming out can increase top speed and fuel efficiency on
calm water.
For shallow water navigation, the engine can be manually tilted to a
maximum angle of 66 degrees, allowing operation in water depths that
would otherwise be inaccessible. The steering system provides 40 degrees
of rotation in both directions, offering excellent maneuverability at
low speeds and during docking.
0Proper propeller selection is essential for maximizing the performance
and efficiency of the Yamaha 40VEO. The engine is designed to operate
within its full throttle RPM range of 4,500 to 5,500, and the propeller
pitch must be selected so that, with a normal boat load, the engine
reaches the upper portion of this range at wide-open throttle. Yamaha
offers a comprehensive range of three-blade aluminum propellers in
various diameters and pitches to accommodate different boat types and
applications.
Available propeller options include 3 x 10 x 15, 3 x 10-1/4 x 14, 3 x
10-3/4 x 16, 3 x 10-3/4 x 17, 3 x 10-3/8 x 13, 3 x 10-5/8 x 12, 3 x
11-1/8 x 13, 3 x 11-1/4 x 14, 3 x 11-3/8 x 12, 3 x 11-5/8 x 11, 3 x
11-3/4 x 10, 3 x 12-1/4 x 9, 3 x 12 x 11, and 3 x 12 x 12. Lower pitch
propellers provide quicker acceleration and better load-carrying
capability, making them suitable for heavier boats or watersports
applications. Higher pitch propellers deliver increased top speed for
lighter, faster craft.
Overall length: 670 mm (26.4 in)
Overall width: 349 mm (13.7 in)
Overall height (short shaft): 1,192 mm (46.9 in)
Overall height (long shaft): 1,319 mm (51.9 in)
Overall height (extra long shaft): 1,433 mm (56.4 in)
Transom height (short shaft): 381 mm (15.0 in)
Transom height (long shaft): 508 mm (20.0 in)
Transom height (extra long shaft): 635 mm (25.0 in)
Weight (short shaft): 74.5 kg (164 lb)
Weight (long shaft): 77.3 kg (170 lb)
Weight (extra long shaft): 80.5 kg (177 lb)
After first 10 hours or 1 month: Check and adjust carburetor
synchronization and ignition timing. Retighten all cylinder head bolts,
crankcase bolts, and engine mounting bolts. Change gear oil.
Every 50 hours or 3 months: Inspect and clean spark plugs, adjusting gap
to 0.9-1.0 mm (0.035-0.039 in) if necessary. Check and clean fuel
filter. Inspect fuel lines and primer bulb for cracks or damage. Check
gear oil for water contamination and change if necessary. Lubricate all
control linkages and moving parts.
Every 100 hours or 6 months: Clean and adjust spark plugs or replace if
worn. Clean cooling water passages and inspect thermostat operation.
Check condition of sacrificial anodes on engine and lower unit. Check
and adjust carburetor settings and idle speed.
Every 200 hours or 1 year: Replace spark plugs with specified NGK
B7HS-10 or BR7HS-10. Replace water pump impeller. Inspect and clean
entire fuel system, including carburetors. Check and adjust reed valve
condition. Replace fuel lines if hardened or cracked. Perform thorough
check of all electrical connections and controls. Change gear oil
regardless of condition.
Cylinder head bolt (1st step): 15 Nm (11 lb-ft)
Cylinder head bolt (2nd step): 28 Nm (20 lb-ft)
Engine unit bolt: 21 Nm (15 lb-ft)
Flywheel nut: 110 Nm (80 lb-ft)
Reed valve bolt: 1 Nm (0.7 lb-ft)
Spark plug: 25 Nm (18 lb-ft)
Propeller nut: 30 Nm (22 lb-ft)
Lower unit bolt: 40 Nm (29 lb-ft)
Propeller shaft housing bolt: 16 Nm (11 lb-ft)
Tiller handle mounting nut: 38 Nm (27 lb-ft)
Steering friction mounting nut: 20 Nm (14 lb-ft)
Tiller handle pivot bolt: 38 Nm (27 lb-ft)
Muffler bolt: 21 Nm (15 lb-ft)
Exhaust manifold bolt: 21 Nm (15 lb-ft)
Exhaust guide bolt: 21 Nm (15 lb-ft)
The Yamaha 40VEO is a versatile outboard engine suitable for a wide
range of boats and applications. Its three-cylinder design provides
smooth power delivery ideal for fishing boats, including bass boats,
aluminum tiller-steered craft, and center console skiffs requiring
reliable 40 horsepower power. The engine performs excellently on small
to medium pontoons and deck boats, where its loop-charged induction
provides the torque needed for carrying multiple passengers. Inflatable
boats and rigid-hull inflatables benefit from the engine's excellent
power-to-weight ratio, making it a popular choice for tenders and rescue
craft.
Commercial users in aquaculture, patrol, and light utility applications
appreciate the engine's durability and the convenience of oil injection
eliminating pre-mixing requirements. The availability of multiple shaft
lengths allows proper fitment on various hull designs, from
shallow-draft fishing boats to deeper-V hulls requiring long or
extra-long shaft configurations. Real-world performance examples include
powering a modified 22-foot cabin cruiser to cruising speeds of 12.5
knots at 3,500 rpm and top speeds of 20 knots at 5,000 rpm. The engine
includes safety features such as an over-rev limiter and overheat alarm
system to protect the powerhead under demanding conditions.
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