Trade-A-Boat — February 2018

Four score

FIVE YEARS ON AND THE YAMAHA F70A STILL HAS NO

DIRECT COMPETITION

talking

outboards

WITH ANDREW NORTON

W

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 the

exhaust 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 turns

150 tradeaboat.com.au