Yamaha 50 HETOL Specifications
| Engine Model: Yamaha 50HETOL |
| Engine Type: 2-stroke inline 3-cylinder gasoline outboard engine |
| Total Displacement: 42.6 cu.in (698 cc) |
| Rated Engine Power: 50 Hp (36.8 kW) at 5000 rpm |
| Fuel System: Carburetor |
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The Yamaha 50 HETOL is a 50-horsepower,
three-cylinder, two-stroke outboard engine, representing a higher output
variant within Yamaha's legendary 50H series. This model is specifically
configured for remote control operation and is equipped with electric
starting and a hydraulic power trim and tilt system, offering boaters a
powerful yet user-friendly package.
Built on a proven three-cylinder architecture, the 50 HETOL is renowned
for its outstanding power-to-weight ratio, robust construction, and the
convenience of its oil injection system, making it a versatile and
dependable choice for a wide array of mid-sized boats.
The Yamaha 50 HETOL is constructed around a proven and efficient
powerhead. It features a 2-stroke, in-line 3-cylinder engine
configuration. The engine displacement is precisely 698 cc (42.6 cu in),
achieved through a bore and stroke of 67.0 mm x 66.0 mm (2.64 in x 2.60
in). This powerhead produces a maximum output of 36.8 kW (50 hp) at
5,000 rpm. The engine is engineered to operate within a full throttle
operating range of 4,500 to 5,500 rpm. The compression ratio is stated
as 6:1.
The power unit of the 50HETOL is engineered for durability and efficient
combustion. The engine uses a loop charge scavenging system to optimize
the fuel-air mixture and exhaust flow.
This loop-charged design creates a circular fuel flow for efficient
transfer of exhaust gas and even distribution of the air-fuel mixture,
resulting in greater combustion efficiency. Intake is managed by a reed
valve system, known for its reliability and precise control of the
air-fuel charge entering the cylinders.
| Fuel System and Lubrication |
The 50 HETOL features Yamaha's advanced Precision Blend oil injection
lubrication system, which automatically injects the precise amount of
oil needed by the motor into the intake manifold during engine
operation. This system eliminates the need to pre-mix fuel and oil,
ensures quick response to the engine's oil demands for reliability, and
minimizes smoke and oil consumption.
The engine is fed by three carburetors (one per cylinder) to ensure
precise fuel metering. The recommended fuel is regular unleaded
gasoline. The engine oil must be a high-quality 2-stroke outboard motor
oil meeting NMMA-certified TC-W3 grade, and it is stored in a dedicated
engine oil tank with a capacity of 1.5 L (1.6 US qt).
The ignition system is a maintenance-free CDI (Capacitor Discharge
Ignition) microcomputer unit, which provides strong spark and precise
automatic electronic advance for optimal performance, preventing plug
fouling, improving starting performance, and reducing maintenance across
the RPM range.
The system includes the Prime Start enrichment feature for effortless
cold starts. The specified spark plugs are NGK B8HS-10 or BR8HS-10. The
charging system incorporates an alternator output of 12V, 6A with a
rectifier/regulator to maintain battery charge for the electric start
and other electrical accessories.
The cooling system is a raw-water, pressure-driven type, drawing water
from the body of water to cool the engine. Exhaust gases are expelled
through the propeller boss for efficient underwater exhaust and noise
reduction, utilizing a Jet System design.
| Mid Section and Lower Unit |
The lower unit is engineered for strength and efficiency. It uses a
spiral bevel gear with a reduction gear ratio of 1.85 (24/13). The gear
shift positions are the standard Forward-Neutral-Reverse (F-N-R),
engaged via a positive-action dog clutch.
The propeller shaft utilizes a spline drive system, and the propeller
direction, when viewed from the rear, is clockwise. The correct
lubricant for the lower unit is hypoid gear oil meeting API GL-4 SAE 90
specifications, with a gear oil capacity of 0.43 L (0.45 US qt).
This outboard is equipped with a hydraulic power trim and tilt system,
allowing for effortless adjustment of the engine angle with the touch of
a button. The trim angle can be adjusted through a wide range, from -4
degrees (tuck/under) to +20 degrees (trim out), enabling the operator to
fine-tune the boat's attitude for optimal performance, fuel efficiency,
and ride quality under various load and water conditions.
For shallow water operation, the system provides a shallow water drive
feature that allows the engine to be quickly set and operated at a
tilted angle for safe navigation, with a maximum tilt-up angle of 69
degrees. The steering angle is 40 degrees to both port and starboard.
To accommodate various boat types and applications, the Yamaha 50 HETOL
can be fitted with a wide selection of aluminum propellers to ensure the
engine operates within its recommended full-throttle RPM range. The
available propeller options, all with three blades, encompass various
diameter and pitch combinations.
These 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.
The Yamaha 50HETOL is available in a long shaft configuration. The
overall length is 670 mm (26.4 in) and the overall width is 360 mm (14.2
in). The overall height is 1,319 mm (51.9 in) with a transom height of
508 mm (20.0 in). The dry weight for this model is 88 kg (194 lb).
Regular maintenance is essential for the longevity of the 50 HETOL. A
critical pre-operation check involves verifying the oil level in the
remote engine oil tank. The gear oil in the lower unit should be checked
regularly for the presence of water or metal particles and changed
according to the manufacturer's schedule, which generally recommends an
initial change after the first 10 hours of operation and then annually
or every 100 hours.
The water pump impeller is a wear item that should be inspected and
replaced periodically, every 1-2 years or if there are signs of reduced
cooling water flow, to prevent overheating. The spark plugs should be
removed, inspected, cleaned, and the gap adjusted annually, and replaced
as needed.
All moving parts, such as steering linkages and tilt tube, require
regular greasing with water-resistant marine grease to prevent corrosion
and ensure smooth operation. Yamaha's unique marine alloy, YDC-30,
provides superior anti-corrosion properties, and strategically placed
aluminum and zinc self-sacrificing anodes offer maximum corrosion
protection.
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 50 HETOL is a versatile power source ideally suited for a
wide range of mid-sized watercraft. Its 50-horsepower output, combined
with the convenience of electric start and power trim and tilt, makes it
a perfect match for bay boats, center consoles, utility boats, and
aluminum fishing boats commonly used on larger inland lakes and coastal
waters.
The proven three-cylinder design delivers excellent response throughout
low and mid-range RPM, achieved through superior exhaust manifold design
and an ideal crankshaft arrangement. The oil injection system and remote
control capabilities provide an elevated level of convenience for
boaters seeking a powerful, easy-to-operate outboard with world-renowned
Yamaha reliability.
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