Yamaha F9.9B Owner's Manual page 42

0–25mm
(0–1in.)
3-3
q
104011
001337
Mount the outboard motor on the center line
(keel line) of the boat, and ensure that the
boat itself is well balanced. Otherwise, the
boat will be hard to steer. For boats without
a keel or which are asymmetrical, consult
your dealer.
1 Center line (keel line)
EMU01298
Mounting Height
To run your boat at optimum efficiency, the
water-resistance (drag) of the boat and out-
board motor must be made as little as pos-
sible. The mounting-height of the outboard
motor greatly affects the water-resistance. If
the mounting-height is too high, cavitation
tends to occur, thus reducing the propul-
sion; and if the propeller tips cut the air, the
engine speed will rise abnormally and
cause the engine to overheat. If the mount-
ing-height is too low, the water-resistance
will increase and thereby reduce engine
efficiency. Mount the engine so that the anti-
cavitation plate is between the bottom of the
boat and a level 25 mm (1 in.) below it.
NOTE:
8 The optimum mounting height of the out-
board motor is affected by the boat/motor
combination and the desired use. Test
runs at different heights can help deter-
mine the optimum mounting height.
8 Refer to the section "TRIMMING OUT-
BOARD MOTOR" for instructions on set-
ting the trim angle of the outboard.
E