Lowrance X-25B User manual

1
X-25BX-25B
X-25BX-25B
X-25B
INSTALLATION AND OPERATION
INSTRUCTIONS

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TABLE OF CONTENTS
INTRODUCTION ..............................................................................................................3
SPECIFICATIONS ............................................................................................................ 3
INSTALLATION................................................................................... 4
INSTALLATION - Bracket .................................................................................................4
POWER CONNECTIONS.................................................................................................5
KEYBOARD BASICS........................................................................................................6
DISPLAY........................................................................................................................... 6
MENUS .............................................................................................................................7
OPERATION....................................................................................... 7
AUTOMATIC .....................................................................................................................7
RANGE .............................................................................................................................8
RANGE - UPPER AND LOWER LIMITS ..........................................................................8
ZOOM ...............................................................................................................................9
SENSITIVITY ...................................................................................................................11
GRAYLINE®...................................................................................................................................................................................................... 12
FISH ID ............................................................................................................................12
FISHTRACK™ .................................................................................................................13
CHART SPEED ...............................................................................................................14
DISPLAY MODE .............................................................................................................. 14
ALARMS ..........................................................................................................................15
LIGHT ..............................................................................................................................16
FEET/METERS................................................................................................................16
DISPLAY CONTRAST ..................................................................................................... 17
ASP (Advanced Signal Processing) ................................................................................. 17
SIMULATOR ....................................................................................................................18
FISH ARCHES.................................................................................................................19
WATER TEMPERATURE AND THERMOCLINES..........................................................20
TROUBLESHOOTING.....................................................................................................21
WARRANTY ....................................................................................................................25
UPS RETURN SERVICE - USA ONLY ...........................................................................26
MISSING PARTS .............................................................................................................28
HOW TO OBTAIN SERVICE - INTERNATIONAL ONLY ................................................29
Copyright © 1995 Lowrance Electronics, Inc.
All rights reserved.
All features and specifications in this manual are subject to change
without notice.
All screens in this manual are simulated.

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INTRODUCTION
ThankyouforpurchasingaLowrancesonar. YourX-25Bisahighquality
sonar designed for both professional and novice fishermen. These units
have an automatic feature that finds and displays the bottom, fish,
structure, and more! All you have to do is press the on key. However, if
youwish to finetune the unit,simply press themenu key. The X-25Bhas
powerful features available through easy-to-use menus.
To get started with your Lowrance unit, first read the installation section.
Thisiswhereitallbegins.Improperinstallationcancauseproblemsdown
the road. After you’ve read the instructions, install the unit, then read the
rest of the manual. The more you know about your unit, the better it will
perform for you. Take this manual for reference when you head for the
water.
NOTICE!
The storage temperature for your unit is from -4 degrees to +167 degrees
Fahrenheit (-20 degrees to +75 degrees Celcius). Extended storage in tempera-
tures higher or lower than specified will damage the liquid crystal display in your
unit. This type of damage is not covered by the warranty. For more information,
contact the factory customer service department or your local service center.
SPECIFICATIONS
Dimensions ...................... 5.9" W x 5.35" H x 3.4" D
Input Voltage.................... 10 - 15 vDC
Current Drain ................... 350 ma (lights off)
........................... 500 ma (lights on)
Transmitter
Frequency.......... 192 kHz
Output Power..... 600 watts (peak-to-peak)
........................... 75 watts (RMS)
Display ........................... 100 pixels (H) x 65 pixels (W)
........................... Supertwist Liquid Crystal Display
5.35"
5.9" 3.4"

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INSTALLATION - Bracket
YoucaninstalltheX-25Bonthetopofadashorfromanoverheadwiththe
suppliedbracket. Itcan alsobe installed in the dash with anoptional IDA-
3 or IDA-4 mounting kit. If you use the supplied bracket, you may be
interested in the optional GBSA-1 swivel bracket kit. This converts the X-
25B'sgimbal bracketto a swivelmount whichcan be used on thedash or
overheadmounting positions. Installationinstructions forthe in-dash and
swivel mounting kits are supplied with the adapter kits.
Mount the X-25B in any convenient location, provided there is clearance
whenit’stiltedforthebestviewingangle.Holesinthebracket’sbaseallow
woodscreworthroughboltmounting.Itmaybenecessarytoplaceapiece
of plywood on the back side of thin panels to reinforce the panel. Make
certain there is enough room behind the unit to attach the power and
transducer cables.
Attach the X-25B to the gimbal bracket using the supplied gimbal knobs
and washers as shown above.
Drill a hole in the dash for the power and transducer cables. The best
locationforthisholeisimmediatelyunderthegimbalbracket.Thisway,the
bracketcovers the hole. The smallest hole the power ortransducer cable
connector can pass through is 3/4". However, you can’t pass a power or
transducer connector and another cable through a 3/4" hole. Therefore,
after drilling the hole, pass the transducer connector up through the hole
fromunderthedash. Thendropthepowercabledownfromthefrontside
of the dash. After installing the transducer and power cables, slide the
bracketoverthehole,thenroutethetransducerandpowercablesoutthe
slot in the back of the bracket. Finally, fasten the bracket to the dash.
GIMBAL KNOB
WASHER
GIMBAL BRACKET
X-25B

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POWER CONNECTIONS
TheX-25Bworksfroma12voltDCsystemonly. Forthebestresults,run
thepowercabledirectlytotheboat’sbattery. Keepthepowercableaway
fromotherboatwiring,especiallytheengine’swires. Thiswillgivethebest
isolation from electrical noise. If the supplied cable is not long enough to
reachthebattery,splice#18gaugeinsulatedwiretoit.Ifyoudoextendthe
powercable,makecertaintoattachthein-linefuseholdersuppliedwiththe
X-25Btothebatteryorpowersource.Thiswillprotectboththeunitandthe
power cable in the event of a short. Use only a 3-amp fuse.
IMPORTANT!
Do not use this product without a 3-amp fuse wired into the power cable!
Failure to use a 3-amp fuse will void your warranty!
You can also attach the power cable to an accessory or power buss,
however, you may have problems with electrical interference.
This units has reverse polarity protection. No damage will occur if the
power wires are reversed. However, the unit will not work until the wires
are attached correctly.
12 VOLT
BATTERY
BLACK
WIRE
RED
WIRE
3 amp
FUSE

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KEYBOARD BASICS
The unit sounds a tone when you
press any key. This tells you the
unit has accepted a command.
ON/CLEAR
Use this key to turn the unit on. It
also clears menu selections and
the menus from the screen.
OFF
This key turns the unit off.
MENU
TheX-25Bhas many featuresthatare accessed withthiskey. To seethe
firstmenu,presstheMENUkey.Toseetheothermenus,presstheMENU
key repeatedly.
UP and DOWN ARROWS
Use these keys to adjust virtually every feature and function on the unit.
NOTE: The up arrow key also stops the chart when no menus are
displayed. In other words, anytime you wish to stop the chart, first make
certainno menu isonthescreen. Nowpresstheuparrowkey. The chart
freezesandtheword“STOP”appearsatthetopofthescreen. Tostartthe
chart, press the up arrow key again.
DISPLAY - General
ThelightsflashforabouttensecondswhentheX-25Bisturnedon. Three
menusappear,oneaftertheother. Themenusarethelights(LAMP),feet-
meterselection(FEET/METER),andcontrastadjustment(DARK/LIGHT).
Toturnthelightson,presstheuparrowkey. Toswitchfromfeettometers,
press the down arrow key when the proper menu appears. To adjust the
contrast, wait for the DARK/LIGHT menu to
appear. Now press the up arrow key to
darkenthescreen, the downarrowtolighten
it. Themenusdisappearafterafewseconds.
If you don’t want to wait, press the ON/
CLEAR key to clear the menus from the
screen.
WhentheX-25Bisfirstturnedon,thedisplay
appearssimilartotheoneatright. Theunitis
in the automatic mode. The depth range
displays on the upper left side of the screen.

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Intheexampleshownatthebottomofthepreviouspage,therangeisfrom
0 to 60 feet and the bottom depth is 34.4 feet.
NOTE:Turning the X-25B off erases all user settings and it returns to the
systemdefaults.Forexample,ifyouturnthelightson,thenturntheunitoff,
the next time you turn the unit on, the lights will be off, since the default
setting for the lights is off.
MENUS
The X-25B uses menus to guide you through the unit’s functions and
features. The menu key accesses these features, allowing you to
customize the unit to your particular needs and water conditions. All you
have to do to leave one menu and enter another is press the menu key
repeatedly. Ifyouevergetlostinthemenus,simplypresstheON/CLEAR
key. This clears the menus from the screen.
Menus change depending on the mode the unit is in. For example, if the
automatic mode is turned off, the sensitivity menu changes from “AUTO
SENS” to “MAN SENS.” Other messages may appear in menu boxes or
new menus can appear, again depending on previous selections.
On the screen shown on the previous page, the lamp menu is showing.
Pressingthe up arrow key while thismenuisonthescreenturnstheback
lights on.
OPERATION
AUTOMATIC
When the X-25B is first turned on, the automatic feature is enabled. This
feature automatically adjusts the unit’s range and sensitivity according to
waterconditions. Italwayskeepsthebottomdepthdisplayedinthelower
portion of the screen.
To turn the automatic feature off, press the
menu key until the AUTO/MAN menu ap-
pears. Now press the down arrow key. This
highlights the letters “MAN.” The unit is now
inthemanualmode. Waitafewsecondsand
the menu will scroll off the screen’s left side.
Pressing the ON/CLEAR key also clears it.
Toturntheautomaticfeatureonagain,repeat
theabovesteps,exceptthistimepresstheup
arrow key.

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RANGE
Youcan’tadjusttherangewhentheX-25Bis
in the automatic mode. It is adjustable when
the unit is in the manual mode, however. To
do so, first put the unit in the manual mode.
Now press the ON/CLEAR key to clear the
screen. Then press the menu key until the
“RANGE SEL” menu appears as shown be-
low. The current range shows at the bottom
ofthemenu. Inthiscase,therangeis60feet.
Now press the up arrow key to decrease the
range, the down arrow key increases the
range. After you select the desired range,
press the ON/CLEAR key to clear the display. If you wait a few seconds,
it automatically clears.
The X-25B has the following ranges:
10, 20, 40, 60, 120, 240, 480, and 900 feet.
and
5, 10, 20, 40, 60, 100, 200, and 300 meters.
NOTE: The depth capability of the X-25B depends on the transducer
installation, water and bottom conditions, and other factors.
RANGE - Upper and Lower Limits
TheX-25Bletsyouchangetheupperandlowerrangelimitswhenit'sinthe
manual mode. This lets you "zoom" in on segments of the water as small
as 10 feet. In other words, you can set the upper limit to 25 feet and the
lowerlimitto35feet,regardlessofthebottom
depth. This in essence, gives you a 10 foot
zoom. You can choose any segment of the
water, as long as the distance between the
upper limit and lower limit is 10 feet (10
meters) or more.
To change the upper limit, first make certain
theunitisinthemanualmode.Next,pressthe
MENU key until the "UPPER LIMIT" menu
appears. Now press the down arrow key to
increasetheupperlimitortheuparrowkeyto
increase it. After you've finished, wait a few

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21 FOOT UPPER LIMIT
secondsandthemenuwillscrolloffthescreen’sleftside. PressingtheON/
CLR key also clears it.
To change the lower limit, again make certain the unit is in the manual
mode.PresstheMENUkeyuntilthe"LOWERLIMIT"menuappears.Now
press the down arrow key to increase the lower limit or the up arrow key
to increase it. When you have the limit set, wait a few seconds and the
menu will scroll off the screen’s left side. Pressing the ON/CLR key also
clears it.
ZOOM
The zoom feature enlarges all echoes on the screen. If the unit is in the
automatic mode, it tracks the bottom signal, always keeping it near the
bottom of the screen. This lets you see small detail, at the same time
enlargingallechoesthatappearonthescreen.
Theunitdoesn’ttrackthebottominthemanual
mode,andtheadjustmentsareslightlydiffer-
ent.
Zoom - Automatic Operation
To zoom the display, first press the MENU
key until the RANGE/ZOOM menu appears
asshownatright. Nowpressthedownarrow
key. This switches the unit into the zoom
mode. Anewmenu immediately appearsas
shown at the top of the next page.

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Thisisthezoomsizemenu. Zoomsizeisthe
distance between the upper limit and the
lower limit. The upper limit shows at the top
leftcornerofthescreen. Thelowerlimitisin
the bottom left corner. For example, if the
upperlimitis 40 feetandthe lower limitis70
feet, the zoom window size is 30 feet. The
word “TRACK” appears in this menu when
you first activate the zoom as shown below.
ThismeanstheX-25Bistrackingthebottom
in a zoom window, always keeping it on the
display.
Press the up arrow key to decrease the zoom size, press the down arrow
key to increase the zoom size.
When the unit is switched into the zoom
mode,theletters“ZM”appearatthetopofthe
screen. Thezoomwindowsizedisplaysinthe
top right corner of the screen.
On the screen shown at right, the zoom size
has been changed to 20 feet.
To turn the zoom feature off, press the menu
key until the RANGE/ZOOM menu appears.
Now press the up arrow key.
This switches the unit into the range mode,
which turns the zoom feature off.
The X-25B has the following zoom ranges:
10, 20, 30, 60, 120, 240, and 480 feet
and
5, 10, 20, 30, 50, 100, and 150 meters.
Zoom - Manual Operation
To operate the zoom feature when the X-25B is in the manual mode, first
pressthemenukey. ThenpressthedownarrowkeyintheRANGE/ZOOM
menu to place the X-25B in the zoom mode. The zoom size menu
automatically appears next. You can change the zoom size by pressing
the up or down arrows. After you select the desired zoom size, press the

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menu key until the “MOVE ZOOM” menu
appears. Thismenuletsyoumovethezoom
windowupordownin onefoot incrementsby
pressingthearrowkeys. Thus,youcanmove
the zoom window up towards the surface,
downtothebottom,oranywhereinbetween.
Thewindowstayswhereyouputit. Itdoesn’t
track the bottom signal.
Toturnthe zoom featureoff,press the menu
key until the RANGE/ZOOM menu appears.
Now press the up arrow key. This switches
the unit into the range mode, which turns the
zoom feature off.
SENSITIVITY
Thesensitivitymenuletsyoucontroltheunit’sabilitytopickupechoes. A
lowsensitivitylevelexcludesmuchofthebottominformation,fishsignals,
and other detail. High sensitivity settings lets you see features, but it can
also clutter the screen with noise and other unwanted signals. Typically,
the best sensitivity level shows a good, solid bottom signal with grayline.
TheX-25Badjuststhesensitivityleveltokeepasolidbottomsignalonthe
screen. It adds a little extra when it’s in the automatic mode. This gives
it the capability to show fish and other detail. However, situations occur
whereitbecomesnecessarytoincreaseordecreasethesensitivitylevel.
Typically, this occurs when you wish to see more detail, so you need to
increasethesensitivity. Theproceduretoadjustitisthesamewhetherthe
unit is in the automatic or manual mode.
Tochangethesensitivitylevel,firstpressthe
menukeyuntilthesensitivity menu appears.
If the unit is in automatic, the menu shows
“AUTOSENS.” Otherwise, themenu shows
“MANSENS.” Nowpresstheuparrowkeyto
increase the sensitivity, the down arrow to
decreaseit. Averticalbargraph in the menu
boxshowsthesensitivitylevel. Echoesscroll-
ingonto the screenwill also showthe effects
of the sensitivity change. If you reach the
maximumorminimumsensitivitylevel,atone
sounds alerting you to the limits.
Afteryou’veadjustedtheunittothedesiredsensitivitylevel,presstheON/

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CLEAR key to clear the display. If you wait a few seconds, it will
automatically clear.
GRAYLINE ®
Graylineletsyoudistinguishbetweenstrongandweakechoes. It“paints”
gray on targets that are stronger than a preset level. This shows the
difference between a hard or soft bottom, large fish versus smaller ones,
or rocks and brush on the bottom. For example, a soft, muddy, or weedy
bottom returns a weaker signal which shows a narrow or no gray line. A
hard bottom returns a strong signal that causes a wide gray line.
If you have two targets of equal size, one with gray and the other without,
the target with gray is the stronger echo. This helps distinguish fish from
structure, or the larger fish from a smaller one.
Grayline ®is adjustable. Since it shows the
differencebetweenstrongandweakechoes,
changing the level may require a different
sensitivity setting.
To change the Grayline level, first press the
MENU key until the Grayline menu appears.
Now press the up arrow key to increase the
level,thedownarrowtodecreaseit. Thebar
graph in the Grayline menu box shows the
levelofGraylinenowinuse. Echoesscrolling
onto the screen will also show the effects of
the Grayline change. If you reach the maxi-
mum or minimum level, a tone sounds alert-
ing you to the limits.
ThelevelchosenbytheX-25Bwhenit’sfirstturnedonisusuallyadequate
formost conditions. Experiment withyour unitto find theGrayline setting
that’s best.
FISH ID FEATURE
The Fish ID feature identifies targets that meet certain conditions as fish.
The microcomputer analyses all echoes and eliminates surface clutter,
thermoclines,andotherundesirablesignals. Inmostinstances,remaining
targets are fish. The Fish ID feature displays symbols on the screen in
place of the actual fish echoes. There are four symbol sizes: tiny, small,
medium,andlarge. Theseshowtherelativesizebetweentargets. Inother

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words,itdisplaysasmallfishsymbolwhenitthinksatargetisasmallfish,
a medium fish symbol on a larger target, etc.
The microcomputer is sophisticated, but it can be fooled. It can't distin-
guish between fish and other suspended objects such as turtles, sub-
merged floats, air bubbles, etc. Individual
treelimbsextendingoutwardsfromagroupof
limbs are the hardest objects for the Fish ID
featuretodistinguishfromfish. Youmaysee
Fish ID symbols on the screen when, in fact,
thereare nofish. Practicewiththeunitwhen
the Fish ID feature is on and off to become
morefamiliarwithFishID.Toturnthisfeature
on, press the menu key until the Fish ID
feature’s menu appears as shown at right.
Now press the up arrow key. This turns the
feature on. To turn it off, repeat the above
steps,but pressthedownarrowkeyinstead.
TheFish ID featurecan’tbe used whenthe X-25B isinthe manual mode.
If you turn the automatic feature off, the Fish ID feature will automatically
be turned off, also.
FISHTRACK™
The X-25B automatically displays the depth of a target when the Fish ID
feature places a fish symbol on the screen as shown below left. This
featureisautomaticallyenabledwhentheX-25Bisturnedon.Toturnitoff
or on again, press the MENU key repeatedly until the Fish Track menu
appears as shown below. Now press the down arrow key to turn it off.
Remember, Fish ID must be on in order to use the Fish Track feature.

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CHART SPEED
The rate echoes scroll across the screen is
called the chart speed. It’s adjustable by
pressing the menu key until the chart speed
menu appears. Chart speed is set to maxi-
mum when the X-25B is first turned on. To
decreaseit,pressthedownarrowkey. Press
theuparrowkeytoincreasethespeedagain.
The bar graph in the Chart Speed menu box
showsagraphofthespeed. Echoesscrolling
onto the screen will also show the effects of
the change. If you reach the maximum or
minimum level, an warning tone sounds.
Tostopthechart,firstclearanymenufromthescreenbypressingtheON/
CLEARkey. Youcan’tstopthechartwhileamenuisdisplayed. Nowpress
the up arrow key. The chart will freeze and the word “STOP” appears at
the top right portion of the screen. To start the chart, press the up arrow
key again.
DISPLAY MODE
TheX-25Bhasthreedifferentscreenmodes.
Tochangemodes,presstheMENUkeyuntil
the “DISP MODE” (Display Mode) menu ap-
pears. Thenpresstheupordownarrowkeys
untilthedesiredmodenumberappears. The
modes are as follows:
CHT 1 (Chart #1)
1. Automatic On
2. Fish I.D. Off
3. Digital depth display On.
CHT 2 (Chart #2)
ThisistheHighSpeedScrollmode. Ithasthe
followingfeatures:
1. Automatic Off
2. Fish ID Feature Off
3. All Digital Displays Off

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Digital
This is the digital only screen. It shows the
digitaldepthdisplayatthetopofthescreenin
very large numbers. The shallow and deep
alarm settings are displayed beneath the
digitaldepth. Nochartshowsonthisscreen.
ALARMS
FISH ALARM
The Fish Alarm sounds a tone when a fish
symbol appears on the screen. To use the
fishalarm,pressthemenukeyuntilthe“FISH
ALARM” menu appears on the screen. Now
press the up arrow key to turn the alarm on.
Repeattheabovestepstoturnthefishalarm
off.(Note:IftheFishIDfeatureisoff,itwillbe
turned on when you turn the fish alarm on.)
DEPTH ALARMS
The depth alarms are triggered only by the
bottom signal. No other echoes will activate these alarms. The depth
alarmsconsistofashallowanddeepalarm. Theshallowalarmsoundsan
alarmtonewhenthebottomgoesshallowerthanthealarm’ssetting. The
deepalarm sounds a tone when the bottom goes deeperthan it’ssetting.
Both alarms adjust the same, although through different menus.
Shallow Alarm
Tosettheshallowalarm,pressthemenukey
repeatedly until the “SHAL ALARM” menu
appears. Press the down arrow key to in-
creasethe shallow alarm's depth setting, the
uparrowkeydecreasesit. Thenumberinthe
shallowalarm’smenubox shows thecurrent
shallow alarm setting. When the number
reaches the desired setting, release the ar-
row key. When the bottom depth goes shal-
lower than the alarm’s setting an alarm tone

16
sounds. Atthe same timethealarm sounds,
a message box appears on the screen as
shown at right.
Press the up arrow key to silence the alarm.
This will turn the alarm sound off until the
shallow alarm is triggered again.
Toturnthealarmoff,pressthemenukeyuntil
theshallowalarmmenuappears. Thenpress
the up arrow key until the word “OFF” ap-
pears.
Deep Alarm
The deep alarm adjusts the same as the shallow alarm. Use the “DEEP
ALARM” menu to adjust the deep alarm. When the bottom signal goes
deeper than the setting, an alarm tone sounds.
LIGHTS
The X-25B’s display is backlighted for night
use. Toturnthebacklightsonoroff,pressthe
menu key repeatedly until the LAMP menu
appears. Now press the up arrow to turn the
lights on or the down arrow to turn them off.
The menu will clear automatically after a few
seconds.
FEET/METER
The X-25B can show the depth in feet or
meters When the unit is in the metric mode,
alldepthreadings,ranges,zooms,andalarm
settings are in meters. When a unit is in the
feetmode,alloftheabovesettingsareinfeet.
Tochange fromfeet tometers orvice-versa,
press the menu key until the FEET/METER
menuappears as shownatthe bottom ofthe
previous page. Press the down arrow key to

17
switchtometric,theuparrowtoswitchtofeet. Displaysshowinfeetwhen
the unit is first turned on. The menu will clear automatically after a few
seconds or you can press the ON/CLEAR key to clear the screen.
DISPLAY CONTRAST
Theunit’sdisplaycontrastisadjustabletosuitdifferentlightingconditions.
Thiswill helpyouseethescreenfrom differentangles,oratvarioustimes
of the day.
To adjust the contrast, press the menu key
until the DARK/LIGHT menu appears. To
decreaseit,pressthedownarrowkey. Press
the up arrow key to increase the contrast.
The bar graph in the Dark/Light menu box
shows a graph of the contrast. The screen
willalsoshowtheeffectsofthechange. Ifyou
reachthemaximumorminimumlevel,atone
sounds alerting you to the limits. The menu
willclearautomaticallyafterafewsecondsor
presstheON/CLEARkeytoclearthescreen.
ASP (Advanced Signal Processing)
ASP is a program embedded in the X-25B’s computer that is specifically
designed to eliminate noise. It continually monitors the signals from the
receiver,determineswhichechoesarenoiseandrejectsthem. Thisallows
true target echoes to display on the screen
with a minimum of clutter. This feature is
especially useful since it typically lets you
operatetheboatatallspeedswithoutadjust-
ingthesensitivityorothercontrols. Whenthe
X-25B is first turned on, ASP is enabled. To
turn ASP off, press the menu key repeatedly
until the ASP menu appears. Now press the
uparrowtoturnitonorthedownarrowtoturn
it off. The menu will clear automatically after
a few seconds or you can press the ON/
CLEAR key to clear the screen.

18
SIMULATOR
TheX-25Bhasasimulatorbuiltintoitthatcan
show a simulated bottom signal with fish. All
featuresoftheX-25Bworknormallywhenthe
simulator is in use. You can change the
range,zoom,andusethealarmsasdesired.
To use the simulator, press the menu key
repeatedly until the SONAR SIM menu ap-
pears. Now press the up arrow to turn it on.
Repeat the above steps to turn it off, or turn
the unit off and back on again.

19
A
BOAT'S DIRECTION OF TRAVEL
A
C
B
BC
FISH ARCHES
Fish arches are created when the cone of sound passes over a fish.
The distance to a fish when the cone first strikes it is shown as "A"
below. When the center of the cone strikes the fish, the distance is
shorter as shown "B". As the cone leaves the fish, the distance in-
creases again as shown in "C".
When the Fish I.D. mode is off, the depth of the water will affect the size
and shape of the fish arch due to the cone angle diameter. For example,
if the cone passes over a fish in shallow water, the signal displayed on
the X-25B may not arch at all. This is due to the narrow cone diameter
and the resolution limitations of the display.
Very small fish probably will not arch at all. Medium sized fish will show
a partial arch, or a shape similar to an arch if they’re in deep water.

20
Large fish will arch, but turn the sensitivity up in deeper water to see the
arch. Because of water conditions, such as heavy surface clutter,
thermoclines, etc., the sensitivity sometimes cannot be increased
enough to get fish arches.
One of the best ways to get fish arches is to expand or “zoom” a
segment of the water. For example, from 45 to 60 feet. The smaller the
segment, the better the screen resolution will be. The easiest way to do
this on the X-25B is with the Zoom feature. This feature expands the
echoes, making it easier to see detail. For the best results, turn the
sensitivity up as high as possible without getting too much noise on the
screen. In medium to deep water, this method should work to display
fish arches.
If you see fish signals when the unit is in the manual mode, but don't get
fish symbols when Fish I.D. is on, try increasing the sensitivity.
WATER TEMPERATURE AND THERMOCLINES
Water temperature has an important-if not controlling-influence upon the
activities of all fish. Fish are cold blooded and their bodies are always
the temperature of the surrounding water. During the winter, colder
water slows down their metabolism. At this time, they need about a
fourth as much food as they consume in the summer.
Most fish don’t spawn unless the water temperature is within rather
narrow limits. The surface temperature meter built into the X-25B helps
identify the desired surface water spawning temperatures for various
species. Trout can’t survive in streams that get too warm. Bass and
other fish eventually die out when stocked in lakes that remain too cold
during the summer. While some fish have a wider temperature toler-
ance than others, each has a certain range within which it tries to stay.
Schooling fish suspended over deep water lie at the level that provides
this temperature. We assume they are the most comfortable here.
The temperature of water in the lake is seldom constant from top to
bottom. Layers of different temperatures form, and the junction of a
warm and cool layer of water is called a thermocline. The depth and
thickness of the thermocline can vary with the season or time of day. In
deep lakes there may be two or more at different depths. Thermoclines
are important to fishermen because they are areas where fish are active.
Many times bait fish will be above the thermocline while larger game fish
will suspend in or just below it.