Operation
32
4. Mount the outboard motor on the center
line (keel line) of the boat, and ensure
that the boat itself is well balanced. Oth-
erwise the boat will be hard to steer. For
boats without a keel or which are asym-
metrical, consult your dealer.
EMU26921
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 possi-
ble. 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 propulsion;
and if the propeller tips cut the air, the engine
speed will rise abnormally and cause the en-
gine to overheat. If the mounting height is too
low, the water resistance will increase and
thereby reduce engine efficiency. Mount the
outboard motor so that the anti-cavitation
plate is between the bottom of the boat and a
level 25 mm (1 in.) below it.
CAUTION:
ECM01630
●
During water testing, check the buoyan-
cy of the boat, at rest, with its maximum
load. Check that the static water level on
the exhaust housing is low enough to
prevent water entry into the power head
when water rises due to waves when the
outboard is not running.
● Incorrect engine height or obstructions
to the smooth flow of water (such as the
design or condition of the boat, or ac-
cessories such as transom ladders or
depth finder transducers) can create air-
borne water spray while the boat is
cruising. If the motor is operated contin-
uously in the presence of airborne water
spray, enough water could enter the en-
gine through the intake opening on the
cowling to cause severe engine dam-
age. Eliminate the cause of the airborne
water spray.
1. Center line (keel line)
ZMU01760
1
U6AU11E0.book Page 32 Friday, September 7, 2007 10:51 AM
©2019 Yamaha Motor Corporation, U.S.A.
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