MH
MOTORHEADJoystick Piloting for Inboards (JPI), from
Mercury Marine, makes docking easi-
er for boats powered by single or twin
inboards. JPI relies on bow and stern
thrusters for yaw control and coordinates
with the thrust from the prop to achieve
the same 360-degree control we’ve come
to expect from joystick systems connect-
ed to steerable propellers.
Mercury debuted JPI aboard Sea Ray’s
SLX-W 230, and I trialed the system re-
cently at DuSable Harbor on the Chicago
lakefront. Sea Ray pitches the SLX-W to
families anxious to join the wakesurfi ng
craze. Its inboard prop is buried safely
under the hull, but the nonsteerable
prop also makes it less agile at low speeds
than the same boat with a
sterndrive. For $10,000 add-
ed to the boat’s $107,000 base
price, the issue is solved by JPI.
My demo boat was powered
by a 370 hp MerCruiser 6.2L
ECT TowSport engine, but JPI
can be rigged with any Mer-
Cruiser gas or diesel inboard
that is equipped with DTS
(Digital Throttle and Shift).
Vetus 25-kilogram-force
thrusters were mounted
at the bow and transom,
but a boatbuilder could
also opt for Side-Power
thrusters. Everything
is tied together with the
brainpower of Mercury
SmartCraft, which coordi-
nates controls through a joystick mount-
ed on the Sea Ray above the throttle.
Dockside, I was able to rotate the boat
within its length, draw straight abeam tothe dock, or crab the boat on
any heading. The thrusters
proved typically noisy, and
there is also no modulation
of the thrusters’ power; they
are either on or off. This re-
quires anticipation in close
maneuvers, but I quickly
got the hang of it.
JPI also proves helpful
when loading on a trailer.
Picking up a fallen rider no
longer requires making a big
turn and bobbing through
the wake. With JPI, simply
chop the throttle and exe-
cute a quick joystick 180 to
head back to the swimmer. JPI will also
make it easier to hold the boat in place
while a boarder gets organized
for takeoff.
The Skyhook station-keeping
feature of other Merc joystick
systems is not available with
JPI because, though each
thruster has its own battery,
the power draw of the thrust-
ers is much greater than the
charging capacity of the al-
ternator. Battery life and
thermal protection lim-
it thrusters to eight to
10 minutes in continuous
use, not enough for practi-
cal Skyhook function.
Mercury JPI also only
works with a MerCruiser
engine. We think JPI adds
enough value to the inboard
experience that tow-sports boatbuilders
aligned with other engine brands may
consider either off ering MerCruiser
power or developing proprietary systems.PHOTOS: (FROM TOP) BILL DOSTER, COURTESY MERCURY MARINE, COURTESY SUZUZKI MARINEMERCURY
JOYSTICK
PILOTING
FOR
INBOARDS
A docking aid for boats
powered by inboard engines
SUZUKI DF9.9BEL
When contributor Tom Schlichter put together the “ultimate jon boat” (visit boatingmag
.com/ultimate-jon-boat), a tournament-ready fish boat that would be economical and
easily launched, he powered it with Suzuki’s DF9.9BEL featuring electric start, lean-burn
technology, and batteryless electronic fuel injection. Schlichter reports reliability and
great economy. $3,396; suzukimarine.com —Kevin FalveyIN CONTROL
Lean it over, twist
it, or do both simul-
taneously to make
your boat dance.