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BASIC OPERATION > USING THE MAIN MENU
Fishfinder 250/250C Owner’s Manual 29
The following settings are available:
• Water Type—allows you to select either Fresh or Salt to
ensure accurate readings on the unit. Sound waves travel at
different rates through each type.
• Depth Number—controls the efficiency of the digital depth
update rate. Fast Sonar Update updates quicker and is
recommended for low-noise, deeper water (>50 ft.). Auto is
best for shallow water or high noise areas, has a slower screen
update, and is best used if you travel a wide variety of depths.
If the unit is unable to track the bottom for any reason, the
digits in the depth window flash on and off to alert you.
• Automatic Scroll Speed Limit—matches the scroll rate
(page 19) to the speed of your vessel (if equipped with a
speed sensor or receiving GPS NMEA input). Entering
your maximum cruising speed will produce a 100% scroll
rate when you reach that speed. One half of that speed will
produce a 50% scroll rate, etc.
• Keel Offset—allows you to offset the surface reading for the
depth of a keel in order to measure depth from the bottom of
your keel instead of from the transducer’s location. Enter a
positive number to offset for a keel. Enter a negative number
to compensate for a large vessel that may draw several feet of
water. The Keel Offset is reflected in the depth reading.
Transducer at surface
Enter a positive (+) Keel Offset
number to show the depth
from the bottom of the keel.
Transducer at bottom of keel
Enter a negative (-) Keel Offset number to
show the depth from the surface.
• Transducer Type—allows you to specify what type of
transducer you are using, if you are not in Simulator mode.
Do not use User Defined unless instructed to do so.
• Calibrate Water Speed—appears only if you are using a
speed-capable transducer/sensor. Calibration is required
to ensure that the Water Speed displayed on your unit is
accurate. The unit automatically uses GPS ground speed (if
available via NMEA input) for comparison on the calibration.
If a GPS ground speed is not available, use either your boat’s
speedometer reading (not always accurate) or a stopwatch to
determine your speed over a certain distance (distance / time
= speed). It is recommended that the calibration take place in
water having little or no current.