Yamaha F70LA Specifications
| Engine Model: Yamaha F70LA |
| Engine Type: 4-stroke inline 4-cylinder SOHC 16-valve gasoline outboard engine |
| Total Displacement: 60.8 cu.in (996 cc) |
| Rated Engine Power: 70 Hp (51.5 kW) at 5800 rpm |
| Fuel System: Electronic Fuel Injection (EFI) |
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The Yamaha F70LA is a 70-horsepower,
four-stroke outboard engine that has redefined expectations in the
midrange power class by delivering exceptional power-to-weight
performance within a remarkably lightweight and compact package.
Introduced in 2010, this model quickly established itself as one of
Yamaha's premier motors, distinguished by its advanced 16-valve, inline
four-cylinder powerhead, electronic fuel injection, and power trim and
tilt, providing operators with responsive acceleration, quiet operation,
and precise control over boat attitude for optimized handling and fuel
efficiency.
The F70LA is built upon a proven 996cc platform, weighing a mere 119 kg,
making it not only the lightest four-stroke 70 horsepower outboard but
also lighter than competitive two-stroke direct-injected outboards in
its class.
Its advanced four-stroke design ensures cleaner operation with reduced
emissions, while features like the Prime Start system, high-output
alternator, and shallow water drive enhance user convenience and expand
operational capabilities across a wide variety of recreational and
semi-commercial applications, from aluminum fishing boats to small
center consoles and pontoon boats.
The Yamaha F70LA is a 4-stroke, Single Overhead Camshaft (SOHC), inline
4-cylinder engine featuring a 16-valve configuration with four valves
per cylinder. The total displacement is 996 cc (60.8 cu.in), achieved
through a bore and stroke of 65.0 mm (2.56 inches) and 75.0 mm (2.95
inches), respectively.
It produces a maximum prop shaft output of 51.5 kW, equivalent to 70
horsepower, at 5,800 rpm. The engine has a full throttle operating range
of 5,300 to 6,300 rpm. The idle speed is set between 700 and 800 rpm.
The compression ratio is 9.4:1.
The powerhead is built upon a robust cylinder block designed for
longevity and smooth operation, utilizing an advanced powerhead design
where pistons and valves are up to 10 percent lighter compared to
previous models. The cylinder head incorporates a Single Overhead
Camshaft (SOHC) operating four valves per cylinder - two intake and two
exhaust - for optimized breathing and combustion efficiency, with total
intake valve area increased by 17 percent.
The valve clearances are critical for performance and must be maintained
within specified ranges. 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, and the engine utilizes a Long Span Mounting
System with large specially constructed rubber engine mounts placed as
far apart vertically and horizontally as possible to achieve smooth and
quiet operation with strength and durability.
The fuel system is a sophisticated Multi-Point Electronic Fuel Injection
(EFI) system, managed by a reliable Engine Control Module via input from
an array of on-engine sensors that control fuel delivery for clean and
efficient performance. The system automatically adjusts the fuel mixture
for varying conditions, with injectors located just above the intake
valves to enhance fuel atomization for more efficient combustion.
All air entering the engine block is routed through a single throttle
valve to ensure the precise amount of air necessary for optimum power
and fuel efficiency, then enters each cylinder through individual long
intake tracks that are pulse tuned to provide air at the precise volume
and timing for maximum density and power. The F70 derives maximum power
from fuel by using Vapour Reduction and Vapour Burning Systems,
eliminating vapour from the fuel rail and re-routing it back to the
Vapour Separator Tank so only fuel is injected into cylinders for better
combustion.
The engine operates on regular unleaded gasoline with a minimum octane
rating of 87, and an ethanol blend limit of 10 percent maximum. A
standard remote fuel tank has a capacity of 25.0 liters (6.6 US
gallons). The engine features a large, on-engine water separating fuel
filter with a water sensor used in conjunction with Yamaha's optional
boat-mounted 10-Micron Water Separating Fuel Filter to separate water
and contaminants from fuel before reaching injectors.
The F70LA 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 outboard motor oil, with Yamalube 4-M FC-W 10W-30
being the preferred brand.
Acceptable oil types include SAE 10W-30 or 10W-40 viscosities that meet
API service classifications SE, SF, SG, SH, SJ, or SL. The total engine
oil capacity is 2.5 liters total, with 2.1 liters (2.2 US quarts)
required when replacing the oil filter and 1.9 liters without filter
replacement during routine maintenance.
Cooling is managed by a raw-water system with thermostatic control,
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.
The thermostat helps maintain acceptable cylinder temperatures across a
wide range of engine speeds. 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 hub
for quieter operation and reduced back pressure, with water-cooled
labyrinth exhaust routing. Engine exhaust is routed through a maze
before exiting above the waterline through the idle exhaust relief
outlet for unbelievably smooth and quiet operation. The gear shift
positions are forward, neutral, and reverse.
The gear ratio is 2.33:1, derived from a 28/12 gear set, providing
excellent torque multiplication for rapid acceleration and improved
performance with heavier loads. The reduction gear type is spiral bevel
gear, and the clutch is a dog type, providing positive engagement with
specially hardened pinion, forward, and reverse gears for increased
durability.
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 0.67 liters
(0.70 US quarts). The mid-section incorporates Yamaha's large
anti-splash plate to help keep water from splashing up between the
leading edge of the outboard and the boat, resulting in a much dryer
ride.
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 +16 degrees,
allowing operators to optimize boat attitude for acceleration, fuel
economy, and ride comfort under varying load and water conditions.
The negative trim settings allow for improved acceleration and the
ability to bring the boat onto the plane more quickly. The tilt-up angle
is 65 degrees. The system also features a shallow water drive
capability, allowing the engine to be quickly tilted and operated at a
shallower angle for safe navigation through shallow water without
striking the bottom. The steering angle is 40 degrees from center in
either direction.
Selecting the correct propeller is essential for achieving optimal
engine performance within the recommended full throttle operating range.
The Yamaha F70LA utilizes a spline drive system and is designed to run
with a wide selection of aluminum and stainless steel propellers.
Performance testing has documented successful operation with propellers
including a 13.5-inch diameter by 15-inch pitch aluminum propeller
achieving a top speed of 30.34 knots at 6000 rpm , a 13-1/8 x 16-inch
Talon stainless steel propeller reaching 40.2 mph at 6000 rpm, and
various other three-blade configurations ranging from 11 to 17 inches in
pitch depending on boat application and performance requirements.
Yamaha offers multiple propeller series including Alloy White K Series
for lightweight boats, Alloy GP K Series with Shift Dampener System for
improved acceleration, Aluminium SDS K Series for heavier hulls, and
Performance Series 3/4 Blade stainless steel props for specialized
applications.
The appropriate propeller allows the engine to operate at or near the
top of its 5,300-6,300 rpm full throttle range when the boat is properly
loaded. Propeller markings indicate the diameter and pitch in inches;
for example, a propeller marked "13-1/8 x 16" indicates a 13.125-inch
diameter and 16-inch pitch.
The overall length of the outboard is 698 mm (27.5 inches). The overall
width is 386 mm (15.2 inches). The overall height for the long shaft
model, designated for a 20-inch transom, is 1,476 mm (58.1 inches), with
a corresponding transom height of 534 mm (21.0 inches).
An extra-long shaft version (F70LX) is available with an overall height
of 1,590 mm and transom height of 648 mm (25.5 inches). The dry weight
for the long shaft version is approximately 114 to 119 kg (253 to 262
lbs), making it the lightest engine in its power class and 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 TCI (Transistor Controlled Ignition)
ignition system with microcomputer control, which provides precise spark
timing without moving parts for reliable, maintenance-free operation.
The alternator output is a robust 12V - 15A to 17A system with a
rectifier/regulator to maintain proper battery charging, with 9A
dedicated to battery charging capacity.
The standard spark plug for the F70LA model is an NGK LKR7E. The spark
plug gap must be maintained between 0.8 and 0.9 mm (0.031 to 0.035
inches). Maximum fuel consumption at 5,800 rpm is approximately 22.5
liters per hour, with optimal cruise economy at 4000 rpm achieving
approximately 10.1 liters per hour. The Variable Trolling RPM feature
allows operators to precisely adjust the engine's trolling speed from
620 to 900 rpm in 50-rpm increments for precise speed control at low
speeds.
The engine is compatible with Yamaha's Command Link digital network
gauges, including the 6YC colour HD LCD gauge and round 6Y8 gauges,
allowing operators to monitor critical engine parameters including
speed, fuel management, trim level, battery voltage, and engine hours in
real time.
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 using feeler gauges. The recommended
battery specification for reliable starting includes appropriate cold
cranking A as specified in the owner's manual.
Adhering to correct torque specifications is critical during assembly
and maintenance to ensure proper sealing, component retention, and safe
operation. The spark plug must be torqued to 17 Nm (12.5 lb-ft) to
ensure proper seating without damaging the cylinder head threads. The
propeller nut, which secures the propeller to the propeller shaft,
requires 34 Nm (25 lb-ft). The engine oil drain plug must be tightened
to 27 Nm (20 lb-ft) to prevent leaks while allowing future removal.
The oil filter requires 18 Nm (13.5 lb-ft) for proper sealing against
its mounting surface. Additional torque specifications for critical
fasteners, including cylinder head bolts, crankcase bolts, connecting
rod cap bolts, flywheel magnet nut, oil pressure switch, ignition coil
bolt, starter motor bolt, power unit bolt, and lower unit bolts, are
documented in the official Yamaha service manual and require precise
multi-stage torquing procedures for proper engine assembly and
maintenance.
The Yamaha F70LA 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 70-horsepower output makes it suitable
for a wide range of boats, including aluminum fishing boats such as the
Stessco Renegade 480, utility skiffs, pontoons, small center-console
vessels like the Biscayne 16'4" and Avid 18 Commander, and as auxiliary
power for larger sailboats. The engine has been documented performing
effectively on boats ranging from 16 to 19 feet in length with gross
weights varying from 879 to 1,721 lbs as tested.
The long shaft configuration is specifically designed for boats with a
20-inch transom, while the extra-long shaft version accommodates 25-inch
transoms. Performance testing has demonstrated outstanding holeshot
capability, with the F70LA accelerating from rest to 40 km/h in 8.43
seconds on a near-ton boat, and achieving 0-20 mph in as little as 5.67
to 6.31 seconds depending on application.
The engine's lightweight design relative to its power output makes it
particularly attractive for vessels where weight distribution is a
concern, and its fuel efficiency of up to 3.35 km per liter at optimum
cruise provides extended range for fishing and recreational activities.
Proper installation, including correct remote control cable adjustment
and battery selection, is essential to ensure safe handling and prevent
loss of control. The optional Yamaha Customer Outboard Protection
(Y-COP) system adds an extra layer of security against unauthorized use.
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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