Yamaha F250 Owners Manual

Operation
35
EMU26930Mounting height (boat bottom)
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...

Operation
36
EMU31800Fuel

Check to be sure you have plenty of fuel for
your trip.

Make sure there are no fuel leaks or gaso-
line fumes.

Check fuel line connections to be sure they
are tight.

Check the water in the fuel filter with the wa-
ter separator warning device. Place the
gear shift lever in neutral and turn the main
switch to “”(on). If the buzzer sounds and
the water separator warning indicator
blinks, consult your Yamaha dealer imme-
diately.
EMU31710Controls

Check throttle, shift, and...

Operation
37
changing in recent years in response to con-
cerns about pollution and resulting emissions
regulations. One of the most obvious changes
has been the elimination of lead from most fu-
els.
As gasoline has changed, the amount of addi-
tives such as aromatics and oxygenates has
increased. These additives are important for
the engines in passenger cars, but they can
have detrimental effects in marine engines,
because of increased deposits in the combus-
tion chamber. When enough deposits...

Operation
38
2. Attach the engine stop switch lanyard to
a secure place on your clothing, or your
arm or leg. Then install the lock plate on
the other end of the lanyard into the en-
gine stop switch.
WARNING
EWM00120

Attach the engine stop switch lanyard to
a secure place on your clothing, or your
arm or leg while operating.

Do not attach the lanyard to clothing
that could tear loose. Do not route the
lanyard where it could become entan-
gled, preventing it from functioning.

Avoid accidentally...

Operation
39
EMU27670
Warming up engineEMU30031Electric start models
1. After starting the engine, allow it to idle for
3 minutes to warm up. Failure to do so will
shorten engine life.
2. Be sure the low oil pressure warning indi-
cator remains off after starting the en-
gine.
3. Check for a steady flow of water from the
cooling water pilot hole.
CAUTION:
ECM01341

If the low oil pressure warning indicator
blinks after the engine starts, stop the
engine. Otherwise serious engine dam-
age could occur....

Operation
40
back to neutral. If this occurs, stop the en-
gine, shift to neutral, then restart the en-
gine and allow it to warm up.
To shift out of neutral
1. Pull the neutral interlock trigger up (if
equipped).
2. Move the remote control lever firmly and
crisply forward (for forward gear) or back-
ward (for reverse gear) about 35° (a de-
tent can felt).
To shift from in gear (forward/reverse) to neu-
tral
1. Close the throttle so that the engine
slows to idle speed.
2. After the engine is at idle...

Operation
41
2. Remove the key if the boat will be left un-
attended.
NOTE:
The engine can also be stopped by pulling the
lanyard and removing the clip from the engine
stop switch, then turning the main switch to
“” (off).
EMU27861
Trimming outboard motor
The trim angle of the outboard motor helps
determine the position of the bow of the boat
in the water. Correct trim angle will help im-
prove performance and fuel economy while
reducing strain on the engine. Correct trim an-
gle depends upon the...

Operation
42
Adjust the outboard motor trim angle using
the power trim and tilt switch.
To raise the bow (trim-out), press the switch
“” (up).
To lower the bow (trim-in), press the switch
“” (down).Make test runs with the trim set to different an-
gles to find the position that works best for
your boat and operating conditions.
EMU27911Adjusting boat trim
When the boat is on plane, a bow-up attitude
results in less drag, greater stability and effi-
ciency. This is generally when the keel line of
the boat...

Operation
43
Bow Down
Too much trim-in causes the boat to “plow”
through the water, decreasing fuel economy
and making it hard to increase speed. Operat-
ing with excessive trim-in at higher speeds
also makes the boat unstable. Resistance at
the bow is greatly increased, heightening the
danger of “bow steering” and making opera-
tion difficult and dangerous.
NOTE:
Depending on the type of boat, the outboard
motor trim angle may have little effect on the
trim of the boat when operating.
EMU27942
Tilting...

Operation
44
4. Push the tilt support knob into the clamp
bracket or pull the tilt support lever toward
you to support the engine.
WARNING
EWM00260
After tilting the outboard motor, be sure to
support it with the tilt support knob or tilt
support lever. Otherwise the outboard mo-
tor could fall back down suddenly if oil in
the power trim and tilt unit loses pressure.
5. Models equipped with trim rods: Once the
outboard motor is supported with the tilt
support lever, press the power trim and
tilt switch /...