Four score
FIVE YEARS ON AND THE YAMAHA F70A STILL HAS NO
DIRECT COMPETITIONtalking
outboards
WITH ANDREW NORTONW
hat
makes the
Yamaha
F70A
unique
is that it weighs less than
its FT60D counterpart, yet
has significantly more
top-end torque and power.
It’s the only four-stroke
outboard in its power range
that can be considered a
repower alternative for older
fibreglass runabouts (such
as the Haines Hunter 445R)
fitted with a two-stroke
Johnson 70 or Yamaha 70B.
The 75hp four-strokes are
simply too heavy.
My local Yamaha dealers
have told me that since its
release in 2010 the F70A
has been very popular with
repowers of older boats, so
Yamaha sure has scored
here!THE NITTY GRITTY
At first glance the F70A
could be mistaken for being
an uprated version of the
FT60D. It has the same base
engine and gear ratio but
that’s where the similarity
ends. Instead of two valves
per cylinder there are four,though still operated by a
single belt-driven overhead
camshaft and compact
rocker arms. Because at
18.7mm the exhaust valve
diameter is less than that in
the FT60D the two valves
only need one rocker arm
to actuate them. At 24.5mm
the intake valve diameter is
much greater so one rocker
arm per valve is needed.
Three rocker arms operating
four valves. Very clever!
To cope with higher
electrical needs over the
FT60D a 17amp voltage
regulated alternator is
fitted, still a bit light in my
opinion. But another clever
touch is that if the engine
management system picks
up a sensor failure other
sensors can compensate
until a laptop computer is
connected and the fault
diagnosed. Yamaha’s Y-COP
(Yamaha Customer Outboard
Protection) off ers remote
keypad starting but make
sure it’s attached to a
small float!
The EFI system is tuned
to run on standard 91 RON
unleaded and as there’s
no oxygen sensor in theexhaust passages, opting for
premium 95 RON won’t give
any performance benefits
(although I’d use it anyway
as it’s a better quality fuel
and less likely to have some
ethanol in it). At least if stale
fuel of less than 91 RON is
detected the ignition timing
will retard to compensate.
The trolling rpm can be
altered in increments of 50.
As with the FT60D
powerhead access is very
good and the engine oil
dipstick and canister oil
filter are easily reached.
Yamaha’s own FCW
(Four Cycle Watercooled)
SAE 10W30 engine oil is
recommended and the 2lt
sump provides adequate
absorption of oil dilution
that occurs during extended
trolling periods. Valve
clearance adjustments are
done with a feeler gauge and
spanner. The recommended
servicing intervals are every
100 hours or annually after
the first 20 hours and the
camshaft timing belt should
be replaced every
1000 hours.
The warranty coverage is
four years.ON THE WATER
Damn! Neither demo engine
gave my flab a workout
but at least my tinnitus
was given a break. Both
engines started instantly
hot or cold without a whiff
of oil smoke and warmed
quickly from cold. Yamaha’s
remote control boxes had
precise shifting without any
clunks, and providing the
antiventilation plates were
kept at least three-quarters
immersed power astern was
good, useful for backing
off shoals. But because
maximum torque appears
to be developed around
4500rpm (the rpm limiter
activates at 6500) the F70A
needs careful propping to
deliver its full potential.
Mounted on a relatively
light aluminium side
console the first engine
I tested had pretty good
holeshot, though on a
fibreglass cuddy cabin the
second engine was a bit
sluggish out of the hole. But
it was pushing a total of
1100kg, a fair load for any 70,
so this was to be expected.
Both engines refused to
ventilate through tight turns150 tradeaboat.com.au