Yamaha F70LB Specifications
| Engine Model: Yamaha F70LB |
| 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 F70LB is a 70-horsepower,
four-stroke, in-line four-cylinder outboard engine, representing a
refined evolution within Yamaha's lightweight and powerful F70 series.
This model is configured for remote control operation and is equipped
with electric starting and a hydraulic power trim and tilt system,
offering boaters a sophisticated, powerful, and exceptionally smooth
experience.
Built on an advanced 996cc platform, the F70LB is renowned for its
class-leading power-to-weight ratio, quiet operation, outstanding fuel
efficiency, and the seamless response of its Electronic Fuel Injection
system, making it a versatile and dependable choice for a wide array of
boats including aluminum fishing boats, pontoons, and lightweight
fiberglass craft.
The Yamaha F70LB is constructed around a refined and efficient
powerhead. It features a 4-stroke, SOHC, in-line 4-cylinder, 16-valve
engine configuration. The engine displacement is precisely 996 cc (60.8
cu in), achieved through a bore and stroke of 65.0 mm x 75.0 mm (2.56 in
x 2.95 in).
This powerhead produces a maximum prop shaft output of 51.5 kW (70 hp)
at 5,800 rpm. The engine is engineered to operate within a full throttle
operating range of 5,300 to 6,300 rpm, with a specified engine idle
speed of 700-800 rpm. The compression ratio is stated as 9.4:1.
The power unit of the F70LB is engineered for durability, efficiency,
and smooth power delivery. The advanced powerhead design features a
single overhead camshaft (SOHC) with four valves per cylinder,
maximizing power and efficiency. Total intake valve area is increased,
while the pistons and valves are lighter, giving it substantially more
horsepower-per-litre of engine displacement than competitive outboards.
The overhead camshaft design efficiently exchanges intake and exhaust
gases for responsive power and fuel efficiency. 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.
It then enters each cylinder through individual long intake tracks,
which are 'pulse tuned' to provide air at the precise volume and timing
for maximum density and power. The valve train requires periodic
adjustment, with specified valve clearances of 0.15-0.25 mm (0.006-0.010
in) for the intake valves and 0.25-0.35 mm (0.010-0.014 in) for the
exhaust valves when the engine is cold.
The F70LB features Yamaha's advanced Electronic Fuel Injection (EFI)
system, which precisely meters fuel for optimal combustion under all
conditions. Four individual compact electronic fuel injectors deliver
the exact amount of fuel needed for optimum performance and economy.
Controlled by the Engine Control Module via input from an array of
on-engine sensors, their location just above the intake valves enhances
fuel atomization, resulting in more efficient combustion. The F70LB
derives every bit of power available from the fuel by using Vapour
Reduction and Vapour Burning Systems.
By eliminating vapour from the fuel rail and re-routing it back to the
Vapour Separator Tank, only fuel is injected in the cylinders for better
combustion and power. The recommended fuel is regular unleaded gasoline
with a minimum octane rating of 87. The engine is supplied with fuel
from a separate tank.
The lubrication system is a wet sump type, meaning the engine oil is
stored in a sump within the engine. The recommended engine oil is
high-quality 4-stroke outboard motor oil, such as Yamalube 4-M FC-W
10W-30, meeting API SE, SF, SG, SH, SJ, or SL service classifications.
The engine oil capacity with oil filter replacement is 2.1 L (2.2 US
qt).
The cooling system is raw-water with thermostatic control, drawing water
from the body of water to cool the engine. A freshwater flushing device
is integrated for easy maintenance. The F70LB features a new outer
cowling design with an intake air drain system, to easily and
efficiently drain away any water that enters the cowling during normal
engine operation.
Exhaust gases are expelled through the propeller boss for efficient
underwater exhaust and noise reduction, with engine exhaust routed
through a labyrinth before exiting above the waterline through the idle
exhaust relief outlet for smooth and quiet operation.
A large anti-splash plate on the front of the lower mid-section helps
keep water from splashing up between the outboard and the boat for a
dryer ride, particularly beneficial for pontoon boat applications.
The ignition system is a TCI (Transistor Controlled Ignition)
microcomputer unit, providing precise spark timing for reliable starting
and efficient power across the RPM range. The specified spark plugs are
NGK LKR7E, with a required gap of 0.8-0.9 mm (0.031-0.035 in).
The charging system incorporates a high-output alternator of 12V - 17A
with a built-in rectifier/regulator to maintain battery charge for the
electric start and other electrical accessories.
| 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 2.33:1 (28/12) , which
provides outstanding hole shot and acceleration. Specially hardened
pinion, forward, and reverse gears increase durability. 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 0.67 L (0.70 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 to +16 degrees, enabling the operator to fine-tune the boat's
attitude for optimal performance, fuel efficiency, and ride quality
under various load and water conditions.
Negative trim angles improve acceleration and help achieve planing
quickly. For shallow water operation, the system provides a standard
shallow water drive feature, allowing the engine to be operated at a
tilted angle for safe navigation, with a maximum tilt-up angle of 65
degrees. The F70LB utilizes a Long Span Mounting System, which uses
large specially constructed rubber engine mounts placed as far apart
vertically and horizontally as possible for smooth and quiet operation.
The Yamaha F70LB is compatible with a range of propellers to match
various boat types and applications. A propeller size of 13-5/8 x 14
(diameter x pitch) was used during performance testing on an Alumacraft
Classic 165 Sport boat.
Authorized Yamaha dealers can recommend the correct propeller based on
boat hull, load, and intended use to ensure the engine operates within
its recommended full-throttle RPM range of 5,300-6,300 rpm.
The Yamaha F70LB is available in a long shaft configuration. The overall
length is 698 mm (27.5 in) and the overall width is 386 mm (15.2 in).
The overall height is 1,476 mm (58.1 in) with a transom height of 534 mm
(21.0 in). The dry weight for this model is 115 kg (253 lb).
Regular maintenance is essential for the longevity of the F70LB. The
engine oil and oil filter should be changed according to the
manufacturer's schedule. The gear oil in the lower unit should be
checked regularly for the presence of water or metal particles and
changed 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. Valve clearance inspection and adjustment should be performed
at recommended intervals.
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. A large, on-engine water-separating fuel
filter with a water sensor helps separate water and contaminants from
the fuel before they can reach the injectors. Optional Command Link
gauges offer a wealth of information to the operator in order to help
provide efficient and effective operation.
Spark plug: 17 Nm (12.5 lb-ft)
Propeller nut: 34 Nm (25 lb-ft)
Oil drain plug: 27 Nm (20 lb-ft)
Oil filter: 18 Nm (13.5 lb-ft)
The Yamaha F70LB is a versatile power source ideally suited for a wide
range of mid-sized watercraft. Its 70-horsepower output, combined with
the convenience of electric start, EFI, and power trim and tilt, makes
it a perfect match for aluminum fishing boats, bay boats, and utility
boats commonly used on inland lakes and coastal waters. It is a popular
choice for boats such as the Alumacraft Classic 165 Sport, the Scout 177
XSS, and the Chaparral R160.
The engine is also ideal for pontoon boats, where the anti-splash plate
proves beneficial, and for applications where clean and quiet
four-stroke operation is desired. Features such as precise trolling
control, adjustable in 50-rpm increments from 620-900 rpm via optional
Command Link gauges or the optional multifunction tiller handle, make it
excellent for walleye trolling and other slow-speed fishing
applications.
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