Yamaha 50TLR Specifications
| Engine Model: Yamaha 50TLR |
| 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 50TLR is a 50-horsepower,
three-cylinder, two-stroke outboard motor that represents Yamaha's
commitment to reliable and efficient marine power. This model is
specifically configured for remote control operation and features
electric starting, making it an excellent choice for boaters who prefer
console-mounted controls and push-button convenience.
The 50TLR shares the proven 698 cc powerhead architecture with other
Yamaha 50 horsepower models but distinguishes itself with the inclusion
of an automatic oil injection system, eliminating the need for
pre-mixing fuel. The Prime Start enrichment system ensures effortless
cold starts by automatically providing the correct fuel mixture. A 6-amp
alternator keeps the battery charged for electronics and accessories.
The power trim and tilt system provides fingertip control of engine
angle for optimal performance under varying conditions. This engine has
earned a reputation for durability and simplicity, making it a popular
choice for fishing boats, pontoons, and small craft requiring dependable
50 horsepower propulsion.
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: 36.8 kW (50 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 B8HS-10 or NGK BR8HS-10.
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/tilt system: Power trim and tilt.
Trim angle range: -4 to 20 degrees.
Tilt-up angle: 69 degrees.
Steering angle: 40 + 40 degrees.
The Yamaha 50TLR features a robust three-cylinder powerhead engineered
for durability and consistent 50-horsepower output. The cylinder block
houses three cylinders with a bore of 67.0 mm and stroke of 66.0 mm,
producing a total displacement of 698 cc. This three-cylinder
configuration provides inherently smooth operation with overlapping
power pulses that reduce vibration compared to two-cylinder designs.
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 intake system
employs reed valves that 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 crankshaft is precision-balanced to minimize vibration during
operation. The cylinder head is designed with optimized combustion
chamber shapes to promote efficient burning of the air-fuel mixture. The
compression ratio is 6.0:1, appropriate for the two-stroke design and
allowing reliable operation on regular-grade fuels.
The Yamaha 50TLR employs a sophisticated fuel system utilizing three
separate carburetors, one for each cylinder, ensuring precise fuel
delivery and balanced performance across the engine's operating range.
This multi-carburetor setup is essential for achieving the 50-horsepower
output while maintaining smooth operation and responsive acceleration.
A key feature of the 50TLR 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 requires periodic inspection for water or contamination.
Owners report that regular maintenance of the carburetors, approximately
every six months, helps prevent issues related to modern ethanol-blended
fuels. The use of clean, fresh regular unleaded gasoline with a minimum
octane rating of 86 is required for proper engine performance and
longevity. The inclusion of a fuel filter/water separator is recommended
to protect the fuel system from contaminants.
The Yamaha 50TLR features an advanced automatic oil injection system,
representing 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 mounted on the engine, 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.
The system includes an oil level indicator on the engine cowling and an
alarm system that alerts the operator to low oil conditions, 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. Periodic
inspection of the oil tank for water accumulation is recommended as part
of routine maintenance.
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 warning indicator on the digital
tachometer that alerts the operator if cooling water flow is
insufficient or if the engine exceeds safe operating temperatures. The
water pump is a critical maintenance item and should be inspected and
the impeller replaced at recommended intervals.
An important maintenance practice is flushing the cooling system with
fresh water after operation in salt, brackish, or polluted water to
prevent deposit buildup and corrosion. The cooling system includes a
pilot water tell-tale that provides a visual indication of water pump
operation and circulation.
| 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 in the 50-horsepower application. The gear ratio is 1.85:1
(24/13), providing an optimal balance of acceleration and top-end
performance for a variety of boat types.
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 50TLR is equipped with a power trim and tilt system that
allows the operator to adjust the engine angle for optimal performance
and shallow water operation at the touch of a switch. The system
provides a trim angle range of -4 to 20 degrees, allowing fine-tuning of
boat attitude for various loading conditions and water surfaces.
Negative trim angles allow the engine to be trimmed in toward the
transom for improved planing and bow-down attitude, while positive trim
angles provide bow-up attitude for increased top speed and efficiency on
calm water. The maximum tilt-up angle is 69 degrees, enabling shallow
water operation and facilitating beaching, launching, or trailering.
The power trim and tilt system includes switches on the remote control
and on the bottom engine cowling for convenient operation from the helm
or while working around the engine. A tilt support lever provides
mechanical locking for trailering or maintenance. The steering system
provides 40 degrees of rotation in both directions, offering excellent
maneuverability at low speeds and during docking.
Proper propeller selection is essential for maximizing the performance
and efficiency of the Yamaha 50TLR. 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, watersports
applications, or operations requiring frequent planing.
Higher pitch propellers deliver increased top speed for lighter, faster
craft. Consultation with a Yamaha dealer is recommended for selecting
the optimal propeller for specific boat and application requirements.
The propeller nut must be tightened to the specified torque to secure
the propeller properly and prevent damage to the thrust washer or
propeller hub.
Overall length: 670 mm (26.4 in)
Overall width: 360 mm (14.2 in)
Overall height (long shaft): 1,319 mm (51.9 in)
Transom height (long shaft): 508 mm (20.0 in)
Weight (long shaft): 88 kg (194 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. 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. Some owners recommend
carburetor cleaning every six months when using ethanol-blended fuels.
Every 200 hours or 1 year: Replace spark plugs with specified NGK
B8HS-10 or BR8HS-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 50TLR is a versatile outboard engine suitable for a wide
range of boats requiring 50-horsepower propulsion. The remote control
configuration and electric start make it ideal for center console boats,
bass boats, and other craft where console-mounted controls are
preferred. Pontoon boats benefit from the engine's 50-horsepower output,
providing adequate power for family cruising and watersports. The power
trim and tilt system allows easy adjustment for varying loads and water
conditions.
Small to medium aluminum and fiberglass fishing boats perform
excellently with the 50TLR, offering the power needed for quick planing
and efficient cruising. Commercial users in aquaculture, patrol, and
light utility applications appreciate the engine's durability and the
convenience of oil injection. The engine is commonly found on 16 to
18-foot boats, where its 50-horsepower output provides excellent
performance. The 50TLR includes safety features such as a start-in-gear
protection system, overheat warning, and oil level warning to protect
the powerhead under demanding conditions.
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