Jet Drive Engine Mounting, Maintenance, Shift Cable Instruction, Service Info - Yamaha T8 Rigging Manual

Outboard Rigging Guide - 2001
JET DRIVE ENGINE MOUNTING
MAINTENANCE, SHIFT CABLE
INSTRUCTION, SERVICE INFORMATION
Mounting Height
Your Yamaha Jet Drive must be mounted 6" to
7" higher on the transom than propeller-
driven outboards; therefore, optimum mount-
ing for 15" shafts is on a 20" transom; and for
20" shafts, a 25" transom.
The positioning of motor height is important, and
must be done carefully. One-quarter inch above
the optimum location will allow air to enter the
pump and will result in ventilation and power
loss. Too low a setting will result in unnecessary
drag, water spray, and reduction in speed.
The initial height setting is accomplished by plac-
ing a yardstick or other straightedge against the
boat bottom (not the keel). The top of the leading
edge of the water intake is adjusted to line up with
the top edge of the straightedge.
Test Running
CAUTION:
When starting your motor for the first time,
make sure water comes out the small hole at
the rear, starboard side of the motor, just
below the powerhead. If no water exits within
a short period of time, shut off the motor and
consult your dealer.
After making the initial motor-height setting, it is
time to test-run the boat. If ventilation occurs (air
enters the pump, which causes loss of thrust and
motor overrevving), then you must lower the
engine 1/4" at a time until smooth operation is
obtained.
Jet Drive Eng. Mtg., Maintenance,
Shift Cable Instruction, Service Info.
If smooth operation is obtained with the initial
setting, raise the motor in 1/4" steps until ventila-
tion does occur. Then, lower the motor 1/4", and
mark and lock that location. This height setting
will never need to be changed, regardless of the
load being carried.
CAUTION:
Slight ventilation on sharp turns or in rough
water is acceptable, but excessive ventilation is
harmful to both motor and pump and should
be avoided.
The motor tilt pin should be set so the engine is in
a vertical position when the boat is planing. If the
boat rides bow-high, or tends to be stern heavy,
tilt the motor down one step. This will point the
jet stream lower, giving added lift to the stern.
NOTE: If the tilt angle is changed, then the motor
height must be rechecked.
Transom Elevators
In some applications, an elevated transom may be
required for proper motor height. When using a
bolted-on bracket, set the intake height 1/2" below
the bottom of the boat in order to obtain the
widest range of adjustability, as shown.
1. Glue two pieces of 3/4" exterior plywood
together using waterproof glue. Clamp or
nail.
2. Bolt to transom at height shown. Use stain-
less steel or zinc-plated hardware with flat
washers on both sides.
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