Humminbird Fish Finder 425 SX User Manual

OPERATIONS  
MANUAL  
 
TABLE OF CONTENTS  
Section 1: Installation preparation . . . . . . . . . . . . . . . . . . . 2  
Parts Supplied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Installation Overview . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Alternative Transducers and Mounting Methods. . . . . . 4  
Beginning Installation . . . . . . . . . . . . . . . . . . . . . . . . . 5  
Section 2: USING THE 425SX. . . . . . . . . . . . . . . . . . . . . . . 6  
How Sonar Works . . . . . . . . . . . . . . . . . . . . . . . . . . . 6  
Simulator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 6  
What You See On Screen . . . . . . . . . . . . . . . . . . . 7–12  
Control Functions . . . . . . . . . . . . . . . . . . . . . . . . 12–15  
Menu Functions . . . . . . . . . . . . . . . . . . . . . . . . . 15–25  
Section 3: ADVANCED FEATURES. . . . . . . . . . . . . . . . . . . 25  
Using Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . . . . 25  
Section 5: MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . 27  
Maintenance and Troubleshooting . . . . . . . . . . . . 27–30  
Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31  
 
INSTALLATION PREPARATION  
PARTS SUPPLIED  
PARTS SUPPLIED  
Before installing your 425SX, please ensure the following parts are included in  
the box:  
425SX fishfinder  
Transducer with 6m (20') of cable and mounting hardware kit  
• Mounting system and mounting hardware kit  
• 2m (6' ) power cable  
• Publications kit  
+
Note: The 425SX includes speed and temperature sensors with  
appropriate hardware and instructions for installation.  
If any of these items are missing contact your local dealer.  
ACCESSORIES  
Humminbird offers a wide assortment of accessories that complement and  
expand the capability of your new 425SX. These accessories are designed with  
the same high standards. The Humminbird Accessory catalog included with  
your unit contains descriptions of the many accessories available and ordering  
information. All Humminbird accessories are available through your full-service  
Humminbird dealer.  
INSTALLATION OVERVIEW  
The 425SX consists of two primary components to install: the control head and  
the transducer.  
The control head contains the sonar transmit and receive circuitry, as well as the  
user controls and display. It should be installed in a location that provides access  
to the controls and visibility while in use. The control head mounts on a quick  
disconnect mounting system that swivels and tilts, providing flexibility for  
viewing from almost anywhere on the boat.  
2
 
INSTALLATION PREPARATION  
INSTALLATION OVERVIEW  
The transducer converts electrical energy from the transmitter into mechanical  
pulses or sound waves. The transducer also receives the reflected sound waves  
and converts them back into electrical signals for display on the control head. It  
should be installed in contact with the surface of the water in an area that has  
smooth water flow - usually on the transom of the boat. There are several  
mounting options for the transducer. Review  
the following section to determine the  
method that works for you and your boat.  
Determining How to Mount the  
Transducer  
The 425SX includes a model XT-6-24  
transducer. This transducer can be mounted  
on the transom of the boat, or bonded to  
the inside of a fiberglass hull boat.  
The transom installation, which is the most  
widely used, places the transducer on the  
outside of the boat hull. This technique  
Transom Mounted Transducer  
produces the least signal loss, and provides a  
way to adjust the transducer after  
installation. The mounting hardware  
included is designed to protect both  
the boat and the transducer should the  
boat strike debris in the water or when  
trailering.  
As an alternative to transom mounting,  
it is possible on many fiberglass-hulled  
boats to glue the transducer on the  
inside of the boat hull. Since fiberglass  
has similar sonar characteristics as  
water, the sonar signal can pass  
through the boat hull with minimal  
loss. The hull of the boat must be single  
layer construction (not double-hulled).  
Also, any air trapped in the lamination  
of the fiberglass would prevent the sonar  
Inside the Hull Mounted Transducer  
3
 
INSTALLATION PREPARATION  
ALTERNATE TRANSDUCERS AND MOUNTING METHODS  
signal from passing through.  
Inside the hull installations require no holes to be drilled into the boat and  
through experimentation, high-speed operation comparable to transom  
mounting can be achieved. Two part, slow cure epoxy is required to glue the  
transducer in place.  
ALTERNATE TRANSDUCERS AND MOUNTING METHODS  
The 425SX comes with everything necessary for installation and operation on  
most boats. However, there are several situations which may require a different  
type of transducer. Inboard boats, wood or metal hulls, and sail boats create  
unique transducer mounting needs. Alternate transducers and mounting  
methods are detailed below.  
Portable Mounting  
The standard transducer can be adapted for  
portable installations using part number MHX-PT2.  
This accessory adapts your transducer to a suction  
cup mount for temporary installation on the boat  
hull or other surface.  
Trolling Motor Mounting  
The standard transducer can also be adapted to  
mount on most trolling motors using part number  
AD-STM-7. This accessory includes a bracket and  
hose clamp that allows mounting the transducer to  
the body of most trolling motors.  
TRANSDUCER EXCHANGE  
Other transducers are available as replacements for the standard transducer.  
You may exchange your new and unassembled transducer for another type by  
returning it to the address listed in Customer Support. Some transducers may  
have additional costs. Refer to the Accessory catalog or call Customer Support  
for information.  
4
 
INSTALLATION PREPARATION  
BEGINNING INSTALLATION  
BEGINNING INSTALLATION  
Now that you have determined the transducer mounting method, you can  
begin installation of the 425SX. The fold out installation guide included  
provides detailed step by step instructions for installation of the control head  
and transducer. For transom mount transducer installations, you will need the  
mounting template at the back of this manual.  
In addition to the parts included you need the following for installation and  
operation:  
• A powered hand drill and various drill bits  
• Phillips and flat-head screw drivers  
• A ruler or measuring tape  
• Pen or pencil  
• 12 volt power source (your boats battery)  
• A 1-amp fuse  
• A fuse holder (if you are wiring directly to the boats battery)  
• Silicone sealant (for sealing drilled holes)  
• 2-part, slow-cure epoxy (for inside the hull transducer installations)  
+
Note: If you have purchased the 425SX you will have in addition  
to the parts and instructions above:  
• Speed and Temperature sensors  
• Instructions for installing speed and temperature sensors  
• Appropriate hardware to mount sensors  
5
 
USING THE 425SX  
HOW SONAR WORKS  
HOW SONAR WORKS  
Your Humminbird unit uses sonar to  
locate and define underwater objects,  
define the bottom terrain, as well as  
determine distance.  
Sonar technology is based on sound  
waves. Your Humminbird unit sends out  
a sound wave signal. With this signal it  
determines distance by measuring the  
time between the transmission of the  
sound wave and when the sound wave  
is reflected off an object. Your  
Humminbird uses the reflected signal to  
interpret location, size and composition of an object.  
Sonar is very fast. A sound wave can travel from the surface to a depth of 70m  
(240') and back again in less than ¹⁄₄ of a second. It is unlikely that your boat  
can "outrun" this sonar signal.  
The 425SX is a 200 kHz, single-beam fishfinder. The 200 kHz frequency  
provides excellent sonar resolution (the ability to distinguish small returns or  
returns which are close to the bottom), while providing depth capabilities to  
185m (600’). The shape of the sonar beam is symmetrical and covers an area  
of approximately 24 degrees side to side and front to rear.  
Actual depth capability depends on factors such as bottom hardness, water  
conditions, and transducer installation. Units will typically read to deeper  
depths in fresh water than in salt water.  
SIMULATOR OPERATION  
The 425SX contains a simulator that allows you to use the unit as if you are on the  
water. The simulator is invaluable for learning how to operate the 425SX.  
There are two ways to start the simulator. If the unit is powered off, press and hold  
the POWER button for approximately three seconds until you hear a continuous chirp.  
6
 
USING THE 425SX  
SIMULATOR OPERATION  
The simulator can also be started by selecting  
the Simulator option on the start-up screen  
after you power-up the unit. When this  
screen is shown, simply press the DOWN  
ARROW until “Simulator” is highlighted.  
When the screen times out, the unit will be  
in simulator mode.  
When in simulator operation, the 425SX responds to control inputs as if it is in  
actual operation, so feel free to experiment, or to customize the unit for your  
particular operation.  
To exit Simulator mode, power the unit off.  
FEATURE MEMORY  
If your 425SX is installed with a transducer connected, any changes you make  
to the set-up or User Options (see Control Functions) while in Simulator are  
retained in the units memory. This allows you to use simulator to experiment  
with the various set-up options, and retain your selected settings for normal  
operation.  
If you are using the 425SX in Simulator when no transducer is connected, any  
selected options are lost when the unit is powered off. The 425SX will return  
to Factory Settings, or options selected when last used with a transducer, if no  
transducer is connected.  
IMPORTANT: A transducer must be connected to the 425SX in  
order to retain user settings selected when in simulator mode. If  
no transducer is detected, the unit defaults to pre-selected  
options when powered off.  
What You See On-Screen  
Your 425SX uses a 160 x 160 matrix FSTN LCD display. This display provides  
outstanding viewability in all light conditions over a wide range of  
temperatures.  
7
 
USING THE 425SX  
WHAT YOU SEE ON-SCREEN  
At initial power-up, the 425SX uses settings that were set at the factory. After  
initial use, the 425SX will remember the settings you enter.  
There are several elements on-screen that are common to all modes of  
operation.  
Figure A  
Temperature/Speed.  
The  
initial screen layout takes one  
of two basic forms depending  
on whether the optional  
Temp/Speed  
accessory  
is  
installed. Figure A shows the  
default view when the  
Temp/Speed  
accessory  
is  
installed. Figure B shows the  
default view when the  
Temp/Speed accessory is not  
installed.  
6
Figure B  
Depth. The digital depth  
number shows the water  
depth directly beneath the  
transducer location.  
Bottom Depiction  
Zero Line  
Depth Range. The depth range  
is shown to the right of the screen.  
The upper number is 0 indicating  
the surface of the water. The lower  
number is one of the nine depth  
ranges available that best match  
the depth of the water. As the  
depth of the water changes, the  
range changes as necessary in  
order to retain  
representation on-screen.  
a
bottom  
Water Depth  
Depth Range  
8
 
USING THE 425SX  
WHAT YOU SEE ON-SCREEN  
When in Auto mode, the horizontal line at the top of the screen is the “zero  
line,” representing the surface of the water. Occasionally there is a gap in this  
line. This gap indicates the unit is updating the display even if the bottom is not  
visible on-screen, or if the bottom information is not changing.  
New sonar information appears on the right side of the graphic area of the  
display and moves to the left as new information is displayed. The 425SX  
automatically selects the appropriate depth range to show the depth of water  
beneath the transducer. This range is selected so the bottom representation is  
typically shown about ²⁄₃ down the display.  
Bottom. The graphic depiction of the bottom provides the user with an  
effective tool for understanding the composition of the bottom. The FSTN type  
display uses 4 discrete levels of gray to indicate the intensity of the returned  
sonar signal. The 425SX can display even the smallest sonar returns with light  
gray pixels. Larger returns are displayed with darker shades of gray. If the  
bottom is hard and smooth, the bottom depiction is narrow and dense. If the  
bottom is soft mud or sand, the depiction will be thick and less dense. This  
indicates that much of the signal is absorbed by the soft bottom. If the bottom  
is rocky or rugged in composition, the depiction is of varying density and  
textured in appearance.  
Wave action also affects the bottom  
depiction. The information drawn is  
Surface Clutter  
Rocky Bottom  
a distance measurement, so if the  
boat is moving up and down over  
flat bottom, the bottom depiction  
often appears in regular variations  
that match wave timing.  
Structure. Structure is defined as  
any object physically attached to the  
bottom. The sonar configuration of  
the 425SX is optimized to give the  
most accurate depiction of bottom  
structure possible. Grass, trees,  
stumps, wrecks or other debris are  
accurately displayed, however the  
m
Hard Bottom Soft Bottom  
9
 
USING THE 425SX  
WHAT YOU SEE ON SCREEN  
depiction of these objects varies with boat speed and direction. The best way to  
learn to interpret structure is to operate the 425SX over a variety of known  
conditions and experiment with user functions to best represent those  
conditions on-screen.  
Surface Clutter. Surface clutter is the layer of water near the surface that is rich  
in algae and other growth, and often is aerated by wind or wave action. This  
area of water interferes with sonar transmission and often appears on-screen as  
regular clusters of individual dots near the “0” line.  
Thermoclines. Thermoclines are sharp differences in water temperature. These  
are easily identified by the continuous nature of the return.  
Second Returns. When  
a
Thermocline Second Return  
sonar signal is reflected off the  
bottom back to the transducer,  
there is often enough energy  
left in the signal to be reflected  
off the surface of the water  
back to the bottom a second  
time. Second returns appear as  
a
slightly weaker bottom  
representation exactly twice the  
depth of the primary bottom  
return. The second return is  
most likely to occur in shallow  
water and in areas of relatively  
hard bottom.  
Fish Arches. With Fish ID off, schools of bait fish as well as individual fish  
are clearly visible on the 425SX display. Bait fish appear as "clouds" having  
different shapes and sizes depending on the number of fish and boat  
speed. Individual fish appear as smaller black and gray lines often  
appearing as a "fish arch." A fish arch forms as the boat moves over the  
fish. Due to the transducer beam angle the distance to the fish decreases  
as it moves into the beam, and then increases as it moves out. When the  
window graphs this distance change, an arch appears. The true depth of  
the fish is the top of the arch when the boat is directly over the fish. Boat  
10  
 
USING THE 425SX  
WHAT YOU SEE ON SCREEN  
speed and movement of the fish greatly affect  
the shape of the arch. When moving slowly, a  
fish creates an elongated arch. With the boat  
moving fast the arch appears shorter. A partial  
arch forms when the fish does not move through  
the entire cone angle.  
Fish Arch Diagram  
The 425SX displays structure such as submerged grass, brush, trees and  
wrecks on the bottom. Structure can be distinguished by comparing the  
area just above and below the main bottom return. Usually structure shows  
as areas of dark to light gray on top of a dark bottom contour. The  
appearance of structure is greatly affected by boat speed and direction; to  
repeat the same image it is often necessary to travel the same speed and  
direction over the location where the structure was originally located.  
The 425SX is also capable of showing layers of water having different  
temperatures. These temperature differences, called thermoclines, appear at  
different depths, depending on current conditions. A thermocline typically  
appears as a continuous band of light gray moving across the display at the  
same depth. Thermoclines always appear above the bottom.  
It is important to remember that sonar cannot distinguish between a fish  
and some other object suspended in the water. Regardless of the object the  
sonar detects, each could be drawn as an arch.  
Fish ID. The 425SX uses  
advanced signal processing  
to further evaluate any  
sonar return between the  
surface and the bottom. For  
instance, a small school of  
bait fish usually appears as a  
dense cluster of individual  
dots. If the return meets  
certain additional criteria, a  
fish symbol will be assigned.  
There are three different size  
fish symbols used to indicate  
ID+ Fish Depth  
11  
 
USING THE 425SX  
CONTROL FUNCTIONS  
the intensity of the sonar return. While signal intensity is a good indicator of  
relative fish size, different species of fish have different sonar characteristics, so  
it is not always possible to distinguish fish size between varying species. The  
signal intensity is "normalized" for depth so that a small fish close to the boat  
does not appear as a large fish symbol.  
ID+ adds an additional piece of information to help the user locate fish. On selected  
fish symbols, the digital depth of the designated fish is drawn to help locate the fish  
vertically. This is especially helpful in setting bait depths or for downrigger  
operation.  
CONTROL FUNCTIONS  
The 425SX uses a simple six button keypad for all user input. Press any button  
and an audible “chirp” confirms the control input. If a button has no function or  
is inappropriate for the situation, an audible “error” is heard. The unit sounds  
multiple chirps.  
Power. The Power button powers the 425SX up for normal operation. When the  
unit is on, POWER turns the unit off. POWER can also be used to go directly into  
Simulator mode. To enter simulator, with the unit powered off,  
press and hold POWER for several seconds until a continuous chirp  
is heard.  
Light. LIGHT controls the units display backlight. With the unit  
powered on, press LIGHT once to turn the backlight on “low.”  
Press LIGHT a second time to turn the backlight on “medium,” a  
third time to turn the backlight on “high”, and a fourth time to  
turn the backlight off. The backlight is very effective for low-light  
and nighttime operation. When the backlight is on, the 425SX will  
consume more power than with the backlight off. This is  
important when using the 425SX in a portable configuration  
powered by a separate battery, or when powering the unit from a  
trolling motor battery.  
12  
 
USING THE 425SX  
CONTROL FUNCTIONS  
When powering the unit from a battery such as in portable  
applications, you can prolong the battery life by using the  
backlight at a minimum.  
The three lower buttons, MENU, UP ARROW and DOWN ARROW work together  
to control the 425SX menu-controlled user functions.  
2D View  
View. VIEW selects one of  
several screen configurations or  
“views” possible depending on  
the transducer in use. When  
using the standard transducer,  
without  
the  
optional  
speed/temp sensor connected,  
the VIEW button toggles the  
display between the full-screen  
2D View and the Large Digital  
Readout View.  
6
The 2D View is the default view,  
and the view which is first seen  
at power-up. Pressing VIEW  
again will select the Large  
Digital Readout View, which  
increases the size of key digital  
information so that it can be  
viewed from a great distance.  
Normal 2D information is  
displayed on the right side of  
the display. Pressing VIEW again  
will toggle the display back to  
the 2D view.  
Large Digit View  
When using the standard  
transducer, with the optional speed/temp sensor connected, the VIEW button  
toggles the display between the full-screen 2D View, the Chart View and the  
Large Digital Readout View.  
13  
 
USING THE 425SX  
CONTROL FUNCTIONS  
Chart View  
The Chart View, shows only the  
digital depth readout, leaving  
more screen area for fish  
location and bottom depiction.  
Menu. MENU displays a menu  
on-screen for adjustment. In  
normal operation, pressing  
MENU  
repeatedly  
cycles  
through all available menus. A  
menu remains on-screen for  
several seconds, and can be  
adjusted by using the ARROW  
Menu  
keys. If no adjustment is made in the allotted  
time, the menu disappears. If you want the menu  
to remain on-screen longer press and hold  
MENU—the menu will remain on-screen  
indefinitely. Once you release the menu button,  
the screen will time out. Once a menu times out,  
it is still considered the active menu. Press MENU  
to bring up the last menu used.  
Arrow Keys. The UP ARROW and DOWN ARROW make adjustments to menu  
functions. On the left side of every menu there are UP ARROW and DOWN  
ARROW symbols. The symbols indicate which ARROW button has a function in  
a particular situation. Either one or both ARROW buttons can be used to adjust  
the menu function. A hollow ARROW symbol means the corresponding ARROW  
button has no function. Pressing that button will result in no adjustment and the  
“error” audible will be heard. A solid ARROW symbol means the corresponding  
ARROW button can be used to affect the menu adjustment.  
Abbreviated Menu. The ARROW buttons often can be  
used when no menu is on-screen. In these situations,  
pressing the ARROW button affects the function of the  
active (last-used) menu. This is a short-cut to menu  
Abbreviated Menu  
operation. An abbreviated menu appears on-screen while  
the adjustment is made and times out. A frequently used menu can be  
adjusted very quickly using this technique.  
14  
 
USING THE 425SX  
MENU FUNCTIONS  
After an adjustment is made to a menu function, the menu times out after a few  
seconds and the unit returns to normal operation.  
Menu Layout. All menus use the same basic layout. The heading at the top  
describes the menu function. The UP ARROW and DOWN ARROW symbols to  
the left of the menu indicate which buttons are available for adjustment. In  
menus that have several possible settings, a range of adjustment indicator shows  
the total range available and the current setting.  
Within the menu are the options available. The selected option or current  
setting is highlighted in the black box. If no adjustment is made, this is the  
selected setting. Press an ARROW button while the menu is displayed to select  
another option.  
Several of the menus are multi-step. In some situations if an adjustment is  
made, additional options become available for further adjustment. Examples of  
these multi-step menus are Depth Range, Depth Alarm and Zoom. See the  
detailed description of each function for further explanation.  
Menu Functions  
Heading  
Up Arrow Option  
Arrow Symbols  
Selected Setting  
Down Arrow Option  
Range of Adjustment Indicator  
Sensitivity. The Sensitivity function controls the sensitivity of the sonar  
receiver. The 425SX automatically adjusts the level of  
receiver sensitivity based on a number of factors  
including the depth of the water and the level of  
noise present. Noise can be caused by other  
electronic devices, engines, trolling motors, propeller  
cavitation and hydrodynamic flow among others.  
15  
 
USING THE 425SX  
MENU FUNCTIONS  
The user has the option of  
adjusting the Sensitivity higher  
or lower based on personal  
preference. You can select one  
of 11 sensitivity settings from -  
5 to +5. A setting of 0 (factory  
setting) has no effect on the  
automatic sensitivity control.  
Increasing the sensitivity (+1  
through +5) enables the unit to  
display the information from  
progressively smaller sonar  
returns. By decreasing the  
sensitivity (-1 through -5), the  
unit effectively filters small  
sonar returns.  
High Sensitivity Sensitivity at “0”  
Low Sensitivity  
In murky or muddy water, it is often helpful to reduce the sensitivity. This  
prevents the display from being cluttered with sonar returns from debris or  
suspended particles. In very clear or very deep water, it may be helpful to increase  
the sensitivity since even the smallest sonar return may be of interest to the user.  
To adjust Sensitivity, press MENU repeatedly until the Sensitivity heading is  
displayed. When the Sensitivity menu appears, use the UP ARROW to increase the  
sensitivity, or the DOWN ARROW to reduce sensitivity. To sequence through the  
available settings, press and hold either ARROW button. Release the button at the  
setting you want to select.  
After an adjustment is made, the menu disappears and the new sensitivity setting  
is in affect. If additional time is needed to study a menu, press and hold the MENU  
button and the menu will remain on-screen indefinitely. If you need to make an  
additional adjustment, press the UP ARROW or DOWN ARROW button.  
Depth Range. The Depth Range function controls the vertical distance displayed  
on the graphic area of the display. There are nine depth ranges available. The top  
of the range is always 0, or the surface of the water. Ranges of 0–5, 0–10, 0–20,  
0–40, 0–60, 0–80, 0–110, 0–150, and 0–185 metres and imperial ranges of  
0–15', 0–30', 0–60', 0–120', 0–180', 0–240', 0–360', 0–480', and 0–600'.  
16  
 
USING THE 425SX  
MENU FUNCTIONS  
The range that positions the bottom depiction  
closest to the bottom of the screen, will best utilize  
the available display resolution.  
Using the factory setting of AUTO the 425SX can  
automatically adjust the depth range depending  
on the depth of the water. The unit tries to  
maintain the bottom depiction about ²⁄₃ down the  
total range (for example, in 6 m (20') of water, the  
0-10m (0-30') range would be selected). This  
provides the best display resolution and therefore  
the best target separation possible.  
The Depth Range can be adjusted manually. Press  
MENU repeatedly until the Depth Range menu is  
visible. Two options are available: Auto and  
Manual.  
The manual setting enables you to adjust the  
current depth range setting. The unit no longer  
adjusts the Depth Range to the most appropriate  
range for bottom display. Often, the bottom may  
not be visible on-screen. The digital depth readout  
always determines the depth of the bottom, even if it is not visible on-screen.  
Using manual Depth Range  
control, you can view sonar  
information from the area near  
the surface in greater detail.  
To return to automatic Depth  
Range control, press the  
MENU button until the Depth  
Range menu appears on-  
screen and use the UP ARROW  
to select AUTO.  
6
Depth Range  
17  
 
USING THE 425SX  
MENU FUNCTIONS  
Zoom. The 425SX uses a greatly enhanced Zoom  
capability called “TruZoom” which offers expanded  
information on a select area of sonar information.  
Zoom is similar to Depth Range because it controls the  
range of information displayed on screen. Zoom,  
however, allows for selection of ranges beneath the  
surface so any area of water between the surface and  
the bottom can be enlarged to provide more detailed information. By using the  
full display to show a small area of coverage, the effective display resolution is  
increased, and the units ability to separate close targets is enhanced.  
The Zoom ranges available are dependent on the  
current depth range. In the 5m (15') depth range,  
TruZoom displays a range equal to one half the  
current depth range. In the 10m (30'), 20m (60'), 40m  
(120'), 60m (180'), 80m (240'), 110m (360'), 150m  
(480') and 185m (600') depth ranges, TruZoom  
displays a range equal to one fourth the current depth  
range. The box at the right side of the screen outlines  
the area to be zoomed.  
The 425SX shows Zoom range in conjunction with  
the full depth range. The Zoom range is shown on  
the left side of the screen and full range information  
is shown on the right side of the display. The area  
which is being enlarged by Zoom is indicated by the  
square box. Zoom can either operate automatically,  
in which the Zoom range is constantly adjusted to  
show the bottom, or manually, in which the user  
controls the location of the Zoom range.  
“Automatic” Zoom is especially helpful when looking  
for structure or bottom detail. The “Automatic” Zoom  
keeps the bottom in view even in quickly changing  
terrain. “Manual” Zoom provides detailed information  
of any area from the surface to the bottom.  
18  
 
USING THE 425SX  
MENU FUNCTIONS  
Upper Zoom Limit  
In “Manual” Zoom, the Zoom  
range does not move as the  
terrain changes. To operate  
Zoom, press MENU repeatedly  
until the Zoom menu is on-  
screen. Three options are  
available: “Off” (Factory Setting),  
“Auto” (Automatic bottom  
tracking Zoom), and “Manual”  
(User controlled Zoom range).  
Press the DOWN ARROW once  
to highlight Auto or twice to  
highlight Manual. If Manual is  
selected a submenu will appear  
Lower Zoom Limit  
allowing manual zoom range adjustment. When the menu disappears, full range  
information is displayed on the right as always. The square box indicates the Zoom  
range. In Auto Zoom, the box will move vertically to remain in the general area of  
the bottom return. The left side of the screen is a magnified view of the  
information seen inside the Zoom range box. The upper and lower depth limits of  
the Zoom range are shown on the right side of the Zoom view.  
Note: It is not possible to use Zoom in  
conjunction with the Large Digital View.  
To disable Zoom, press the MENU button until the  
Zoom menu is on-screen. Use the UP ARROW to  
highlight Off, and let the menu time out.  
When the unit is powered off, the Zoom menu  
returns to Zoom Off.  
Depth Alarm. The 425SX contains an audible  
alarm to warn you of shallow water depths. The  
alarm is adjustable to depths of .6m (2') to 30m  
(99'). When the alarm is enabled, an audible alarm  
sounds if the water beneath the boat is equal to or  
less than the selected alarm depth. The alarm  
sounds continuously for about five seconds, and  
19  
 
USING THE 425SX  
MENU FUNCTIONS  
then intermittently to remind you that you are still in shallow water. Additionally,  
the 425SX can anticipate quickly changing terrain and sound the Depth Alarm  
before the bottom depth actually reaches the preset alarm depth.  
Fish Alarm. The Fish Alarm alerts you to the  
presence of fish, or other targets not connected  
to the bottom. The Fish Alarm has three  
different settings that correspond to the three  
different size fish symbols shown on-screen.  
The default setting is “OFF.” With the “Large  
fish only” setting, the 425SX alarms on only  
those targets that are represented by the large  
fish symbols. The 425SX can be set to alarm on  
only large and medium fish, or set to alarm on  
all fish.  
Once the Fish Alarm is enabled, the 425SX emits  
an audible beep when the selected size fish  
symbol appears on-screen. The sound is slightly  
different for each of the three fish symbol sizes, so  
with practice, it is possible to distinguish the size  
of the detected fish without looking at the unit.  
Fish Alarm settings are remembered when the  
unit is powered off.  
Triplog. Triplog provides a running log of  
information based on input from the  
Temp/Speed sensor.  
Since Triplog requires information from  
the Temp/Speed sensor to operate, if this  
sensor is not detected by the 425SX, the  
Triplog menu will not appear as an  
option.  
20  
 
USING THE 425SX  
MENU FUNCTIONS  
Triplog provides four pieces of  
information: the total time  
elapsed since power-up or  
reset, the distance traveled  
since the 425SX was powered  
up or reset, the average speed,  
and the input voltage from  
your boats electrical system.  
The time, speed and distance  
calculations are useful for  
tracking your progress on a  
trip. The input voltage is useful  
Triplog  
for determining the condition of the charging system of the boat. When used  
in a portable application or whenever the 425SX is operated from a battery  
source, the voltage number can be used to determine battery life. The 425SX  
will operate at voltages from 10 to 20 VDC. Voltages in excess of 20 or less  
than 10 VDC cause the unit to power off. The Triplog resets at power off.  
Options. The Options Menu is a series of linked  
menu functions used initially to set your preferences.  
Once your preferences are selected, it is unlikely  
these functions need to be accessed during the  
normal operation of the product. The Option menus  
include: Contrast, Display Speed, Battery Alarm,  
Bottom Black, Fish ID, Numeral size, Units Speed,  
Units Depth, Language, Speed Offset, Depth Offset  
and Reset. Press the view key at any time to exit options and return to normal  
operation.  
Languages. The language menu displays  
available language choices. Included in the 425SX  
are: ENGLISH, FRENCH, ITALIAN, GERMAN, NORWEGIAN,  
SWEDISH, SPANISH, FINNISH, PORTUGUESE, POLISH, DANISH,  
HUNGARIAN AND DUTCH. To select your language,  
push the UP or Down Arrow Buttons to scroll  
through the list.  
21  
 
USING THE 425SX  
MENU FUNCTIONS  
Contrast. The Contrast function allows the user to  
control the level of contrast of the LCD display. The  
425SX will automatically adjust the display contrast  
to compensate for changing ambient temperatures;  
however, some situations may occur where manual  
adjustment will provide a higher level of contrast.  
Eleven contrast settings, +5 to -5, are possible. The  
display contrast will change as the adjustment is made so the optimum level of  
contrast can easily be adjusted. Use the ARROW buttons to highlight the  
desired selection.  
Display Speed. Display Speed controls the rate  
at which the graphic information moves across  
the display. There are 5 possible speeds; the  
fastest rate (5) is the factory setting. If your  
boat is stationary or moving very slowly for  
extended periods, it may be desirable to update  
the display at a slower rate. The closer the  
update rate matches boat speed, the more  
accurate is the graphic depiction of the terrain  
beneath your boat.  
Use the UP and DOWN ARROWS to select the desired update rate. (1) is the  
slowest, (5) is the fastest. Use the MENU button to advance to the next menu.  
The Display Speed setting is remembered when the unit is powered off.  
Battery Alarm. The Battery Alarm Option  
allows you to select the voltage level at which  
the Battery Alarm activates. At the Battery  
Alarm menu (under options), you will note that  
the default setting is OFF. Push the DOWN  
ARROW BUTTON to select the feature ON.  
Push the DOWN ARROW BUTTON again to  
move into the ADJUST BATTERY ALARM setting. Using the UP and DOWN  
ARROW BUTTONS, select a voltage between 9.0 and 12.0.  
22  
 
USING THE 425SX  
MENU FUNCTIONS  
When the voltage drops below your selected voltage, an audible alarm will  
sound, and a battery alarm icon will be  
displayed on screen with current voltage  
level.  
Bottom Black. There are two selections  
available: Off and On. The factory setting is  
Off. With this setting, the 425SX displays the  
bottom using 4 level grayscale. This allows  
you to determine the texture  
and relative hardness of the  
bottom. Selecting Bottom  
Black “ON” causes the unit to  
blacken in the display below  
the bottom. This gives the user  
easiest recognition of the  
bottom location, even from a  
great distance.  
The 425SX remembers the  
Bottom Black setting when  
powered off.  
Bottom Black View  
Fish ID. There are three selections available: Off, ID+  
ON, and Adjust. The factory setting is ID+ OFF. With  
Fish ID Off, sonar returns are displayed as “raw”  
information. There is no interpretation made by the  
unit. Selecting ID ON also enables the fish alarm.  
ID+ On Raw Sonar  
ID+ On enables the 425SX to interpret the raw sonar  
data and, using a variety of techniques, depict  
appropriate target returns as one of three different  
size fish symbols. Further identification shows which  
beam the fish is detected in. The 425SX also displays  
the depth beneath the surface with the  
corresponding fish symbol.  
23  
 
USING THE 425SX  
MENU FUNCTIONS  
Selecting Adjust and making incremental changes  
enhances the fishfinders ability to identify sonar returns  
as fish symbols.  
Increasing the value to a number greater than zero  
shows more fish symbols on-screen. In this case smaller  
sonar returns will be depicted as fish symbols. This is  
useful for identifying many smaller sonar returns (such  
as bait fish) as fish symbols.  
Decreasing the value to a number less than zero shows fewer fish symbols on-  
screen. In this case smaller sonar returns are disregarded. This is useful for  
eliminating many small sonar returns when seeking larger species of fish.  
The 425SX remembers this selection even when the unit is powered off.  
Numeral Size. Two options are available: Big and  
Small. The factory setting is Big. With this setting, the  
digital depth and speed and temp numerals are drawn  
large enough to be read from across the boat. The big  
numerals occupy space on the display that could be  
used for the graphics area. Hence, the small numerals  
option. With small numerals selected, a greater  
amount of the display area is available for the graphic view. This effectively  
increases the display resolution of the unit.  
Numeral Size settings are remembered when powered off.  
Units Speed. Units of Speed allows the selection of  
MPH (statute miles per hour), KTS (nautical miles per  
hour) or KPH (Kilometers Per Hour). Use the Arrow  
buttons to highlight the desired selection.  
Speed Offset. The Speed Offset option allows the  
user to compensate for differences in hull design, and  
its effect on the accuracy of the speed measurement.  
If there is a discrepancy between the indicated speed  
and another speed measurement device on the boat,  
the speed measurement can be varied to improve  
24  
 
ADVANCED FEATURES  
USING DIAGNOSTIC  
accuracy. Remember, the speed paddle wheel measures speed through the  
water, not speed over ground.  
Speed offset is remembered after power is disconnected.  
Depth Offset. The Depth Offset allows the user to select  
the point on the boat from which the depth  
measurement is made. Selecting a positive value adds  
distance to the measurement. If the transducer is  
mounted 1 metre beneath the waterline, a positive 1 will  
show the correct depth from the surface of the water.  
Another frequent use of depth offset is to show the  
depth beneath the deepest point of the hull. A negative  
value equal to the distance from the transducer location  
and the deepest point of the hull will have the same  
effect as mounting the transducer at the deepest point.  
Depth offset is remembered after power is  
disconnected.  
Reset. With the many User Options available to customize the 425SX, it is easy to  
configure the unit in such a way that it is detrimental to a particular use. By using the  
Reset function, all variable or user-controlled features of the 425SX are returned to  
the factory settings.  
The Reset function is an important first step in troubleshooting problems to ensure  
that a user selected setting is not the cause for the perceived problem.  
USING THE DIAGNOSTIC FEATURE  
The 425SX contains a powerful diagnostic  
tool that can aid in determining the cause  
of a problem.  
To use the Diagnostic feature, select the  
Diagnostic feature on the start-up menu of  
the initial screen.  
25  
 
ADVANCED FEATURES  
USING DIAGNOSTIC  
Self Test. Initially, the 425SX will perform a self-test. This test confirms the  
operation of all internal circuitry. At the conclusion of the test, one of two  
messages will appear. PASSED indicates the internal test discovered no  
failures, FAILED indicates a significant internal problem was discovered and  
the unit requires factory service. A code number appears that tells repair  
personnel where the problem is.  
Transducer Connection. The first connection tested is Transducer input. If a  
transducer is detected, the message CONNECTED appears. If a series of dashed  
lines is shown, no transducer is connected or there is a problem with the  
transducer or cable.  
If you are using multiple transducers, switch between transducers to confirm  
the connections for each.  
Voltage Input. Another connection tested is the voltage input, and is  
especially helpful in diagnosing input voltage problems. The current input  
voltage is displayed. If voltage fluctuations or power supply in excess of 20  
VDC or less than 10 VDC is suspected, use the diagnostic screen to confirm  
input voltage. Often, small outboard motors do not effectively regulate  
voltage when operated at high engine speeds.  
Use Diagnostic while running the boat at high speeds to show the voltage  
gain. Also, if you are using the 425SX in portable configuration or from the  
trolling motor battery, Diagnostic can be used to evaluate the health of the  
battery by showing the present voltage.  
Total Time. The total time category indicates the total time the unit has  
been in use since shipped from the factory. It is normal for some hours to  
appear in the total time when the unit is new due to factory testing. While  
this is often of interest to the user, it is primarily a diagnostic tool for the  
repair technician should the unit need service.  
26  
 
ADVANCED FEATURES  
MAINTENANCE/TROUBLESHOOTING  
MAINTENANCE  
Your 425SX is designed to provide years of trouble free operation with virtually no  
maintenance. Follow these simple procedures to ensure your 425SX continues to  
deliver top performance.  
• If the unit comes into contact with salt spray, simply wipe the affected  
surfaces with a cloth dampened in fresh water. Do not use a chemical glass  
cleaner on the lens. Chemicals in the solution may cause cracking in the lens  
of the unit.  
• When cleaning the LCD protective lens, use a chamois and non-abrasive,  
mild cleaner. Do not wipe while dirt or grease is on the lens. Be careful to  
avoid scratching the lens.  
• If your boat remains in the water for long periods of time, algae and other  
marine growth can reduce the effectiveness of the transducer. Periodically  
clean the face of the transducer with liquid detergent. Pivoting the  
transducer up in the bracket may allow better access for inspection or  
cleaning.  
• If your boat remains out of the water for a long period of time, it may take  
some time to wet the transducer when returned to the water. Small air  
bubbles can cling to the surface of the transducer and interfere with proper  
operation. These bubbles dissipate with time, or you can wipe the face of the  
transducer with your fingers after the transducer is in the water.  
• Never leave the 425SX in a closed car or trunk—the extremely high  
temperatures generated in hot weather can damage the electronics.  
TROUBLESHOOTING  
Do not attempt to repair the 425SX yourself. There are no user serviceable parts  
inside, and special tools and techniques are required for reassembly to ensure the  
waterproof integrity of the housing. Repairs should be performed only by  
authorized Humminbird technicians.  
Many requests for repair received by Humminbird involve units that do not  
actually need repair. These units are returned “no problem found.” If you have a  
problem with your 425SX, use the following troubleshooting guide before calling  
your dealer or sending your unit in for repair. The 425SX contains several tools  
that can aid in determining if there is a problem and how to isolate and repair the  
problem in many cases.  
27  
 
ADVANCED FEATURES  
TROUBLESHOOTING  
1. Nothing happens when I turn the unit on.  
Check the power cable connection at both ends. Be sure the cable is connected  
correctly to a reliable power source—red lead to positive, black lead to negative  
or ground. Ensure the power available at the mount is between 10 and 20 VDC.  
If the unit is wired through a fuse panel, ensure the panel is powered. Often  
accessory fuse panels are controlled by a separate switch or the ignition switch.  
Also, often a fuse can appear to be good when in fact is not. Check the fuse with  
a tester or replace it with a fuse known to be good.  
Check the power connection to the 425SX. It is possible to force the power cable  
connector into the cable holder incorrectly. If the connector is reversed, the unit  
will not work. Examine the contacts on the back of the unit to ensure there is no  
corrosion. Finally, ensure the unit is firmly seated on the mount. The electrical con-  
tacts are not made until the unit is fully seated.  
Ensure the metal cable retainer is properly installed in the mount. If not, the power  
connection may push out when the unit is put on the mount.  
2. There is no transducer detected.  
The 425SX has the ability to detect and identify that a transducer is connected.  
First, ensure that an appropriate transducer connector is positioned correctly in  
the connector holder, and that the unit is fully seated on the mount.  
Second, inspect the transducer cable from end to end for breaks, kinks, or cuts in  
the outer casing of the cable. Also ensure the transducer is fully submerged in  
water. If the transducer is connected to the unit through a switch, temporarily  
connect it directly to the unit and try again. If none of these items identifies an  
obvious problem, the transducer itself is probably the problem. Be sure to include  
the transducer if returning the unit for repair.  
3. There is no bottom reading visible on the display.  
There are a number of possible causes for this condition. If the loss of bottom  
information occurs only at high boat speeds, the transducer needs adjusting. If the  
digital depth readout is working but there is no bottom visible on-screen, it is possible  
the depth range has been adjusted manually to a range lower than what is needed  
to display the bottom. Also, in very deep water, it may be necessary to manually  
increase the sensitivity setting to maintain a graphic depiction of the bottom.  
28  
 
ADVANCED FEATURES  
TROUBLESHOOTING  
If you are using a transducer switch to connect two transducers to the 425SX,  
ensure the switch is in the correct position to connect a transducer that is in water.  
(If a trolling motor transducer is selected and the trolling motor is out of water, no  
sonar information appears.)  
If none of the above solve the problem, inspect the transducer cable from end to  
end for breaks, kinks, or cuts in the outer casing of the cable. If the transducer is  
connected to the unit through a switch, temporarily connect it directly to the unit  
and try again. If none of these items identifies an obvious problem, the transducer  
itself may be the problem. Be sure to include the transducer if returning the unit  
for repair.  
4. When in very shallow water, I get gaps in the bottom reading  
and inconsistent digital depth indication.  
The 425SX will work reliably in water .6m (2') or deeper. The depth is measured  
from the transducer, not necessarily from the surface.  
5. The unit comes on before I press POWER, and won’t turn off.  
Check the transducer cable—if the outer jacket of the cable has been cut and the  
cable is in contact with bare metal, you need to repair the cut with electrical tape.  
If there is no problem with the cable, disconnect the transducer from the unit and  
see if the problem is corrected, to confirm the source of the problem.  
6. I get gaps in the reading at high speeds.  
Your transducer needs adjusting. If the transducer is transom-mounted, there are  
two adjustments available to you—height, and running angle. Make small  
adjustments and run the boat at high speeds to determine the effect. It may take  
several tries to optimize high speed operation. This can also be a result of air or  
turbulence in the transducer location caused by rivets, ribs, etc.  
29  
 
ADVANCED FEATURES  
TROUBLESHOOTING  
7. My unit loses power at high speeds.  
Your 425SX has over-voltage protection that turns the unit off when input voltage  
exceeds 20 VDC. Some outboard motors do not effectively regulate the power  
output of the engines alternator and can produce voltage in excess of 20 volts  
when running at high RPMs. The 425SX displays input voltage in the Diagnostic  
screen. Use this readout to determine if the voltage exceeds 20 VDC.  
8. The screen begins to fade out. Images are not as sharp as  
normal.  
Check the input voltage using Diagnostic. The 425SX will not operate on input  
voltages below 10 VDC.  
9. The display shows many black dots at high speeds and high  
sensitivity settings.  
You are seeing noise or interference caused by one of several sources. Noise can  
be caused by other electronic devices. Turn off any nearby electronics and see if  
the problem goes away. Noise can also be caused by the engine. If engine noise  
is causing the interference, the problem will intensify at higher RPMs. Increase the  
engine speed with the boat stationary to isolate this cause. Propeller cavitation  
can appear as noise on-screen. If the transducer is mounted too close to the  
propeller, the turbulence generated can interfere with the sonar signal. Ensure  
that the transducer is mounted at least 38cm (15") from the prop.  
For Service and/or repair of your 425SX please contact your  
local dealer.  
Further information on HUMMINBIRD products can be found at:  
30  
 
SPECIFICATIONS  
Languages supported: Danish, Dutch, English, Finnish, French,  
German, Hungarian, Italian, Norwegian, Polish, Portuguese,  
Spanish and Swedish.  
Operating Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 kHz  
Power Output . . . . . . . . . . . . . . . . . . . . . . . . . 400 Watts (RMS)  
3200 Watts (Peak to Peak)  
Area of Coverage . . . . . . . . . . . . . . . . . . . . . . . . 24° at -10 db  
Power Requirement . . . . . . . . . . . . . . . . . . . . . . . . 10 - 20 VDC  
Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FSTN LCD  
LCD Matrix in pixels . . . . . . . . . . . . . . . . . . . . . . . 160 H x 160 V  
Viewing Area . . . . . . . . . . . . . . . . . . . . . . . . 10cm H x 7.6cm V  
(4" H x 3" V)  
Mounting . . . . . . . . . . . . . . . . . . . . . . Quick Disconnect Mount  
Unit Size . . . . . . . . . . . . . . . . . . 19.4cm H x 20cm W x 11cm D  
(7⁵⁄₈"H x 7⁷⁄₈"W x 4³⁄₈"D)  
Transducer (Standard) . . . . . . . . . . . . . . . . . . . . . . . . . . XT-6-24  
Transducer Cable Length . . . . . . . . . . . . . . . . . . . . 6 metres (20')  
Depth Ranges . . . . 5, 10, 20, 40, 60, 80, 110, 150 & 185 metres  
. . . . . . . . . . . 15', 30', 60', 120', 180', 240', 360', 480', & 600'  
Zoom Ranges . . . . . . . . . . . 2, 5, 10, 15, 20, 28, 38 & 46 metres  
(7¹⁄₂', 15', 30',45', 60', 90', 120', 150')  
31  
 
 
Use this template with transducer mounting bracket 403606  
 
 

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