A
I magine you are the leader of an
engineering team tasked with
creating a new engine. It must be
as light and compact as possible.
It must make strong bottom-end
torque, reach — but not exceed — a
specifi ed peak horsepower rating,
and be able to withstand extended
operation under tremendous load.
It must meet future emissions
and sound standards and be
compatible with a range of controls
and electronics. And here’s the
kicker — you have no idea what
vehicle this engine will power.
This is the very challenging
everyday mission facing marine-
engine designers: Please meet
each of these criteria and, by the
way, your new engine could end
up on a bass boat or a pontoon,
a heavy deck boat or a feather-
weight aluminum skiff. When
an engineering team at Ford
develops a new engine, they know
it’s going to power an F150 truck
that Ford will also manufacture.
That’s a luxury Yamaha engineers
could have only wished for as they
developed the new F90B outboard
motor. At the end of its assembly
line, the outboard is packed in abox and sent out into the world,
duty and destination unknown.
Four of those new F90B
outboards were sent to
boatbuilders participating in a
demo day that Yamaha recently
organized on Geneva Lake in
Wisconsin. We usually pick one
boat for a test of a new motor, but
in this case we were presented
with an opportunity to evaluate
this important new outboard
on a diverse collection of boats.
And so we tested the F90B four
times, on four boats, to fi nd out
if Yamaha was able to create
one new motor capable of many
diff erent missions.A KEY PLAYER
Today’s mega motors might get
all the glory, but the 90 to 115 hp
range represents the heart of the
outboard market, accounting for
a big sales volume that includes
many fi rst-time customers.
These engines represent a critical
chance to make a good fi rst
impression.
The new Yamaha F90B is
based on a 1.8-liter in-line four-
cylinder powerhead that replacesthe previous 1.6-liter F90A. The
bottom of the engine is the same
as the 1.8-liter F115B introduced
in 2014. The key diff erence is the
design of the cylinder head. The
F115B uses a double overhead-
cam head to actuate four valves per
cylinder. The F90B uses a single
overhead-cam head with four
valves per cylinder, a design that
might compromise performance
a bit but is less complex (and
thus less expensive), lighter in
weight and more compact than
the double cam. The F90B is
physically smaller than the F115B
in every dimension — for instance,
a 90 cowl will not fi t on a 115.
Yamaha used some of that space
on the back of the motor to locate
the fuel-vapor separator in a spot
where it will be easy to service.
Yamaha claims more top-
end power and bottom-end
torque from the new powerhead
(compared to the previous
1.6-liter engines), and I would
expect an improvement on the
bottom just from the increase in
displacement. Charging power is
also improved, from 25 peak amps
to 35 peak amps, with about 28
amps available at just 1,000 rpm.
The F90B is not compatible with a
digital control, but the new motor
can be equipped with the Yamaha
Multi-Function Tiller Handle
(sold separately). The motor is
off ered with 20- and 25-inch shaft
lengths, and all versions have a
2.15-to-1 gear ratio. There are
nine diff erent Yamaha aluminum
and stainless-steel props up to 14
inches in diameter off ered for the
F90B, some featuring the Yamaha
SDS (Shift Dampening System)
hub, which provides the fi nal
factor in dialing in performance.PHOTOS: COURTESY YAMAHA, SHUTTERSTOCK (ICONS)TO TEST ITS VERSATILITY, WE RAN THE NEW
YAMAHA F90B ON FOUR VERY DIFFERENT BOATS.
BY CHARLES PLUEDDEMANBOATINGMAG.COM | FEBRUARY 2018| 79