Yamaha F50TLR Specifications
| Engine Model: Yamaha F50TLR |
| Engine Type: 4-stroke inline 4-cylinder OHC 8-valve gasoline outboard engine |
| Total Displacement: 57.1 cu.in (935 cc) |
| Rated Engine Power: 50 Hp (36.8 kW) at 5500 rpm |
| Fuel System: Carburetors |
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The Yamaha F50TLR is a 50-horsepower,
four-stroke outboard engine renowned for its lightweight construction,
fuel efficiency, and quiet operation, making it a favored choice among
anglers and recreational boaters during its production run from the late
1990s through the mid-2000s. This model is distinguished by its electric
start system, remote control steering, and power trim and tilt,
providing operators with effortless command and the ability to precisely
adjust the boat's attitude for optimal handling and fuel economy.
The F50TLR is built upon a 935cc, four-cylinder powerhead delivering
smooth, reliable power, with later iterations of this platform
incorporating electronic fuel injection for enhanced performance. Its
portability, fuel efficiency, and quiet running characteristics made it
exceptionally well-suited for a wide variety of applications, from
aluminum fishing boats to small pontoons and inflatable craft.
The Yamaha F50TLR is a 4-stroke, Overhead Camshaft (OHC), inline
4-cylinder engine featuring an 8-valve configuration. The total
displacement is 935 cc (57.1 cu.in), achieved through a bore and stroke
of 63.0 mm (2.48 inches) and 75.0 mm (2.95 inches), respectively. It
produces a maximum prop shaft output of 36.8 kW, equivalent to 50
horsepower, at 5,500 rpm. The engine has a full throttle operating range
of 5,000 to 6,000 rpm. The compression ratio is 9.3:1.
The powerhead is built upon a robust cylinder block designed for
longevity and smooth operation. The cylinder head incorporates an
Overhead Camshaft (OHC) operating two intake and two exhaust valves per
cylinder for optimized breathing and combustion efficiency.
The valve clearances require periodic inspection and adjustment to
maintain performance. The intake valve clearance is set to 0.15-0.25 mm
(0.006-0.010 inches), while the exhaust valve clearance is set to
0.25-0.35 mm (0.010-0.014 inches). The camshaft and crankshaft are
precision components requiring careful handling during service.
The fuel system is based on four individual carburetors, one for each
cylinder, featuring Yamaha's Prime Start enrichment system for
effortless starting. The engine operates on regular unleaded gasoline
with a fuel rating of 86 to 91 octane. Maximum fuel consumption at 6,000
rpm is approximately 17.3 liters per hour (4.57 US gallons per hour,
3.81 Imperial gallons per hour).
The F50TLR utilizes a wet sump lubrication system, meaning engine oil is
contained within a sump in the powerhead. The recommended engine oil is
high-quality 4-stroke motor oil with SAE viscosities of 10W-30, 10W-40,
or 20W-40 that meet API service classifications SE, SF, SG, SH, or SL.
The total engine oil capacity, including the oil filter, is 2.2 liters
(2.3 US quarts, 1.9 Imperial quarts).
Cooling is managed by a raw-water system with a thermostat, circulating
water through passages in the engine block and cylinder head. A water
pump, driven by the drive shaft, draws water from outside the boat and
forces it through the engine to maintain optimal operating temperatures.
A pilot water outlet on the engine exterior provides a visual indication
that the water pump is functioning and cooling water is circulating
properly. A fresh water flushing system is integrated into the design,
facilitating easy removal of salt and debris after operation in marine
environments.
| Mid Section and Lower Unit |
The exhaust system is designed to expel gases through the propeller boss
for quieter operation and reduced back pressure. The gear shift
positions are forward, neutral, and reverse. The gear ratio is 1.85:1,
derived from a 24/13 gear set. The reduction gear type is spiral bevel
gear, and the clutch is a dog type, providing positive engagement.
The propeller shaft utilizes a spline drive system for secure propeller
mounting, and the propeller rotation, when viewed from the rear, is
clockwise in forward gear. The gear case requires hypoid gear oil
meeting API GL-4 SAE 90 standards, with a total capacity of 0.43 liters
(0.45 US quarts, 0.38 Imperial quarts).
The engine is equipped with a power trim and tilt system, providing
full, relaxed control over the engine's angle relative to the transom.
The trim angle is adjustable within a range of -4 to +20 degrees,
allowing operators to optimize boat attitude for acceleration, fuel
economy, and ride comfort under varying load and water conditions.
The tilt-up angle is 69 degrees. The system also features a tilt support
lever for maintenance and trailering positions. The steering angle is 40
degrees in both directions.
Selecting the correct propeller is essential for achieving optimal
engine performance within the recommended full throttle operating range.
The Yamaha F50TLR utilizes a spline drive system and is designed to run
with a wide selection of aluminum and stainless steel propellers.
Available propeller sizes, listed by diameter and pitch in inches,
include: 10 x 15 aluminum, 10-1/4 x 14 aluminum, 10-3/8 x 13 aluminum,
10-5/8 x 12 aluminum, 10-3/4 x 16 aluminum, 10-3/4 x 17 aluminum, 11-1/4
x 14 aluminum, 10-1/4 x 14 stainless steel, 10-1/4 x 15 stainless steel,
10-1/4 x 16 stainless steel, 10-5/8 x 13 stainless steel, 11-1/4 x 14
stainless steel, 11-1/2 x 13 stainless steel, 11-3/4 x 12 stainless
steel, and 12 x 11 stainless steel.
The appropriate propeller allows the engine to operate at or near the
top of its 5,000-6,000 rpm full throttle range when the boat is properly
loaded.
The overall length of the outboard is 718 mm (28.3 inches). The overall
width is 361 mm (14.2 inches). The overall height for the long shaft
model, designated for a 20-inch transom, is 1,397 mm (55.0 inches), with
a corresponding transom height of 508 mm (20.0 inches). The dry weight
for the long shaft version is 108 kg (238 lbs), reflecting the
lightweight construction that made this model particularly attractive
for vessels where weight distribution is a concern.
Routine maintenance is essential for optimal performance and longevity.
The engine is equipped with a microcomputer CDI ignition control system
with ignition timing ranging from 5 degrees BTDC at idle to 35 degrees
BTDC at wide-open throttle. The alternator output is 12 volts at 10
amperes. The standard spark plug for the F50TLR is an NGK DPR6EA-9.
The engine features a comprehensive warning system monitoring oil
pressure, overheating, and other critical parameters. The maintenance
schedule includes key services at initial break-in, 50 hours, 100 hours,
and annual intervals. Items requiring periodic attention include the
valve clearance, which must be inspected and adjusted by qualified
personnel.
The engine is compatible with Command Link multifunction gauges,
allowing operators to monitor critical engine parameters including
speed, fuel management, and engine hours in real time. The Y-COP
security system is available as an optional feature for theft
protection.
Adhering to correct torque specifications is critical during assembly
and maintenance to ensure proper sealing, component retention, and safe
operation. The M6 cylinder head bolts are tightened in a two-step
process: first to 6 Nm (4.3 lb-ft), and finally to 12 Nm (8.7 lb-ft).
The M9 cylinder head bolts are tightened in a two-step process: first to
23 Nm (17 lb-ft), and finally to 47 Nm (34 lb-ft). The M6 crankcase
bolts are tightened in a two-step process: first to 6 Nm (4.3 lb-ft),
and finally to 12 Nm (8.7 lb-ft).
The M8 crankcase bolts are tightened in a two-step process: first to 15
Nm (11 lb-ft), and finally to 30 Nm (22 lb-ft). The connecting rod cap
bolts are tightened in a two-step process: first to 6 Nm (4.3 lb-ft),
and finally to 17 Nm (12 lb-ft). The flywheel magnet nut is a critical
fastener torqued to 160 Nm (116 lb-ft). The oil pressure switch requires
9 Nm (6.5 lb-ft). The ignition coil bolt requires 7 Nm (5.1 lb-ft).
The starter motor bolt requires 30 Nm (22 lb-ft). The power unit bolt
requires 21 Nm (15 lb-ft). The spark plug must be torqued to 18 Nm (13
lb-ft) to ensure proper seating without damaging the cylinder head
threads. The oil filter requires 18 Nm (13 lb-ft) for proper sealing
against its mounting surface. The drain bolt requires 18 Nm (13 lb-ft).
The lower unit bolt requires 40 Nm (29 lb-ft). The propeller nut, which
secures the propeller to the propeller shaft, requires 35 Nm (25 lb-ft).
The Yamaha F50TLR is intended for use on boats where the total
horsepower does not exceed the vessel's maximum rated power capacity, as
indicated on the boat's capacity plate. Its 50-horsepower output makes
it suitable for a wide range of boats, including aluminum fishing boats,
utility skiffs, pontoons, small center-console vessels, inflatables, and
as auxiliary power for larger sailboats.
The long shaft configuration is specifically designed for boats with a
20-inch transom. The engine's lightweight design relative to its power
output makes it particularly attractive for vessels where weight
distribution is a concern. Users have reported fuel efficiency of
approximately 7.5 miles per gallon with planing speeds around 32-33
miles per hour when operated solo, though performance with additional
passengers requires careful weight distribution for optimal planing.
Proper installation, including correct remote control cable adjustment
and battery selection, is essential to ensure safe handling and prevent
loss of control. As with all outboards, operators must always ensure the
engine stop switch lanyard is attached to a secure part of their
clothing or life jacket.
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