WARNING: DO NOT ATTEMPT TO ADJUST THE
UNIT WHILE YOUR PWC IS RUNNING. SHUT OFF ENGINE, AND
DISCONNECT SAFETY LANYARD WHEN MAKING ADJUSTMENTS.
*Before tuning the Adjust-A-Thrust,
your craft should be in good running order and properly
dialed in. If you are installing the Adjust-A-Thrust as part
of a performance package and have made other modifications
to your motor it is recommended that you dial in your craft
with just the stock tailcone installed. The Adjust-A-Thrust
can put a load on your motor similar to installing a bigger
impeller and can make it hard to dial in your carbs.
TUNING THE ADJUST-A-THRUST
*Remove shuttle, ride craft for 5 to 10
minutes until the motor is thoroughly warmed up. Make a full
throttle run across the lake and note MAX RPM
*Install the shortest shuttle and the short bolt assy and
ride again, note MAX RPM. NOTE Using the short bolt requires
quite a bit of effort to install as the spring is being
*If you don’t lose any RPM, install a longer shuttle and
*Keep trying longer shuttles until you start losing too much
rpm, or stop gaining top speed
*If you are not losing RPM with the longest shuttle, you can
install the long bolt assy. This increases the amount of
shuttle travel, and decreases spring preload, speeding up
the shift. When installing the long bolt assy, it is
recommended that you go down 2 shuttle sizes and resume RPM
tuning with the long bolt. You can also use the extra tuning
washers to preload the spring with either bolt.
*Whichever bolt you end up using for your application, you
MUST use the shuttle stop. It is there to prevent coil
binding in the spring. When adding tuning washers, place
them above the shuttle stop on the bolt. Adding washers
increases the spring rate, which slows down the shift. It
also decreases the total shift length of the shuttle.
*If you lose more than 150 rpm and the craft feels sluggish
in the mid range and low end, the shuttle is too long.
Holding machine at WOT for too long may cause engine
*Best speed is usually found 20 to 70 RPM below MAX RPM.
*4 stroke engines may not lose any rpm, but if you install
too long of a shuttle, then you will lose top speed. Low end
and midrange will be sluggish
*It should be noted that some machines are very sensitive to
nozzle size and motor loading, If you lose to much RPM you
are overloading the motor, and may seize your engine
*If you can’t get the unit dialed in with the shuttles that
came in your kit, contact Wet Wolf Technologies, and we will
set you up with different length shuttles.
* The Adjust-A-Thrust loads the motor similar to installing
a bigger prop. Carbs may have to be adjusted.
*After riding in salt water unit should be flushed. This is
can be done during normal flushing, just make sure to spray
fresh water into the back of the pump.
*When installing the shuttle bolt, turn it in until it
bottoms, then tweak the allen wrench about 3/16 of a turn,
this will snug it up enough so that it wont fall out, but
not enough to break off the threads.
* The screen provided over the inlet orifice is held in with
a small amount of superglue. If the screen gets plugged, it
will flush itself clean when the shuttle backshifts. If the
screen becomes clogged and will not clean itself, it may be
removed and the unit will function normally without the
*Letting off the gas lowers pressure in the pump and lets
the unit backshift into low gear, getting on the gas makes
it upshift again. The more preload on the spring, the faster
the unit backshifts.
The Adjust-A-Thrust is shipped with 4 different length
shuttles. These shuttles are matched to the particular pump
that they are to be installed on. However, there are so many
variables that affect pump performance, that your particular
set-up may require different length shuttles. We stock
shuttles from 2.0” to 4”
in ¼ “ increments.
*Whenever trying different shuttle lengths, always use the
RPM drop method. If the motor won't lose RPM, install a
longer shuttle and try again.
*If you can’t get the unit dialed in with the shuttles that
came in your kit, contact Wet Wolf at (509) 280-5444, and we
will send you different shuttles.
The size of the exit nozzle is one of the factors that
determines a crafts top speed., and how fast it gets there.
The larger the exit nozzle is, the greater the increase in
low end thrust. If you have an adjustable nozzle, you may
want to install a slightly larger ring. (1 - 2MM larger)
High horsepower machines (4 Strokes may wish to do some on
water testing before boring the nozzle.
If you own a selection of impellers, installing a lighter
pitched impeller will allow the engine to rev faster and
increase your low end performance, while maintaining or
increasing top speed
Changes in altitude affect the performance of your PWC. You
may have to adjust carb settings when you change altitude.
The Adjust-A-Thrust should also be adjusted when you change
altitude. The higher you go, the less shift your motor can
pull. Adjust the unit with the RPM drop method whenever you
change altitude to get the most out of your craft.
Many PWC owners are constantly modifying their craft. As you
increase engine horsepower, the unit may be adjusted for
more shift as your engine can pull it.
TYPICAL TUNING SCENARIO:
Modified GTX LTD with skat trak magnum pump with 84mm nozzle
ring installed, goes about 65mph on top end, with good
acceleration, max RPM - 7300. After installing an 87mm
nozzle ring and the Adjust-A-Thrust main body with no
shuttles installed, max RPM went up to 7350, acceleration
greatly improved, but top speed was down 2.5 to 3 mph. After
installing the proper shuttle and tuning the
Adjust-A-Thrust, max RPM came down to 7260, top speed
increased to 66 mph, and there was no loss of that killer
bottom end gained by enlarging the exit nozzle.
*If you bore the exit nozzle, you
should check the size of
the steering nozzle. Generally, the steering nozzle
should be 2 – 3 mm larger than the exit nozzle. If you do
not bore the steering nozzle, thrust centering of the
handlebars will be more noticeable, and it will make it
harder to turn at full throttle.
NOTE For twin
engine jet boats, the additional tuning washers may be used
in one unit to even out RPM between the 2 engines at WOT
Questions or comments, call Wet Wolf
Technologies (509) 280-5444 or e-mail email@example.com
TUNING SHEET 2006
big shuttle revision