Garmin 120 Fish Finder User Manual

Assembling the Transducer
Fishfinder 120
Installation Instructions
A - Fishfinder 120 Sonar Unit (1)
B - Swivel Mount Bracket (1)
C - Swivel Base (1)
D - Mounting Knobs- Short (1), Long (1)
E - Mounting Knob Spacer (1)
F - Transducer With Power Cable (1)
G - Transducer Mount (1)
H - Trolling Motor Mount Gasket (1)
I - 5 mm Flat Washers (2)
K - 10-32 Lock Nut (1)
L - 4 x 12 mm Screws (4)
M - 10-32 x 1.75 Screw (1)
N - 1/4” Cable Clamps (2)
O - Plastic Spacer (1)
P - 1/4” Rubber Washer (1)
Q - Cable Tie, 5.6” (4)
R - Cable Tie, 20” (1)
S - Snap-Ring (1)
(Cable not shown)
DO NOT cut the transducer lead, this will void your warranty and may cause the
unit to not operate at optimal levels.
Do not mount the transducer behind strakes,
rivet lines, struts, fittings, water intakes, or
discharge ports.
DO NOT mount the transducer behind strakes, rivet lines, struts, fittings, water
intake, discharge ports, eroding paint, or anything that creates air bubbles or causes the
water to become turbulent. It is important that the transducer be as close to the center
line as possible in calm, non-turbulent water for optimal performance. Avoid mounting
the transducer in locations where the boat may be supported during launching, hauling, trailering, or storage.
Mount the transducer away from the path of the prop on single drive boats. On
twin drive boats, mount the transducer between the drives if possible. Do not mount
the transducer directly in the path of the prop. The transducer can cause cavitation that
may degrade the boat’s performance and damage the prop.
Unit Installation — Selecting a Proper Location
Choose a location that provides optimal viewing while operating the vessel and
allows easy access to the unit’s keypad. Select a mounting surface strong enough to
support the weight of the unit and protect it from excessive vibration or shock. DO
NOT mount the bracket in a location where the unit is exposed to extreme temperature conditions. When installing the mounting bracket, be sure to allow room for the
connection/routing of the power cable.
Mounting the Bracket Assembly
Tool List (not included) - Drill, Screwdriver (Phillips or Standard), three #8 pan head
machine bolts with matching nuts and washers and a 5/32” drill bit, OR three #8 pan
head self-tapping screws and a 1/16” drill bit
1. Using the swivel base as a template, mark the location of the three holes which
are used to secure the bracket to the mounting surface.
2. If securing the base with machine bolts, drill three 5/32” holes at the locations
you marked. OR, If securing the base using self-tapping
screws, drill 1/16” starter holes at the locations you
marked. Starter holes should generally be no deeper
than half the screw length.
3. Secure the swivel base with three bolts or screws.
4. Place the rest of the mount over the swivel base
and secure with the short knob.
1. Slide the large Cable Tie through slot on the Transducer Mount with the ridges of
the band facing up until equal lengths extend on both sides of the mount. (For
cold water or heavy timber/debris areas, a metal 4-5” worm gear clamp is recommended.)
2. Position the Mount Gasket on the curved top of the Mount.
3. Place the transducer assembly against the motor body of the trolling motor with the
front of the transducer pointed away from the trolling motor propeller.
4. Place the pointed end of Cable Tie through the fastener hole on the
opposite end and pull through (you will hear clicks) until snug.
5. Position the transducer so that it is parallel with the bottom
when in use. Make sure the Gasket is aligned properly. Pull
the Cable Tie end until tight. Excess may be trimmed off if
needed. Tighten the 10-32 locking nut until it touches the
mounting bracket and then tighten 1/4 turn more (do
not overtighten).
6. Route the 20’ (6.1 m) transducer cable using
the supplied cable ties to secure the cable
to the motor shaft. If desired, the forwardfacing portion (except the Cable Tie pocket)
of the Transducer Mount may be filled with
sealant to avoid debris accumulation.
Mounting the Transducer On a Transom
Selecting a Transom Mount Location
For your sonar to operate properly, the transducer has to be located in clean (nonturbulent) water. The transducer should be mounted as near the center of the boat as
Mounting the Transducer On a Trolling Motor
Apply marine sealant to all screw
threads to prevent water from
seeping into the transom.
Mount the transducer parallel with the
water line.
Make sure the transducer is below
water level when the boat is on plane
at high speed.
Installing the Unit On the Mounting Bracket
1. Align the slot on the back of the unit with the long mounting knob and slide in
place. It may be necessary to adjust the long knob to spread the bracket arms
apart. (Turn counter-clockwise to widen the bracket arms, clockwise to tighten.)
2. Adjust the unit angle and tighten the long mounting knob until snug.
3. Tilt the unit by loosening the long knob on the right side of the bracket assembly.
4. Rotate the entire bracket by twisting it left or right. (You will hear clicks as you turn
the bracket.)
5. Tighten all knobs once the desired viewing angle is obtained.
Tool List (not included) - Drill, 3/8" Wrench or Socket, 5/32" and 1/8" Drill Bits,
Masking Tape, #2 Phillips Screw Driver, Marine Sealant
1. Position the transom mount at the selected location, making sure the transducer is
parallel with the water line. Mark the center locations of each hole on the transom
mount. (See figures to the right.)
2. Using the 5/32" bit, drill the pilot holes approximately 1" (25 mm) deep at the
marked locations. To avoid drilling the holes too deep, wrap a piece of tape around
the bit 1" from the point of the bit.
3. Apply Marine Sealant to the 5 x 30 mm screws. Attach the transducer to the transom
using the 5 x 30 mm screws. Adjust the transducer to extend beyond the bottom
of the transom approximately 1/8" (3 mm) on fiberglass hulls or 3/8" (10 mm) on
aluminum hulls. Adjust the transducer to be aligned parallel with the water.
5. Tighten the 10-32 locking nut until it touches the mounting bracket and then
tighten 1/4 turn more (do not overtighten).
6. Place the first cable clamp on the transducer cable approximately one third of the
distance between the transducer and the top of the transom. Mark the location.
Using a 1/8" bit, drill a pilot hole approximately 3/8" (10 mm) deep.
7. Attach the cable clamp using a 4 x 12 mm screw. Coat the screw with marine sealant before installation. Repeat steps 6 and 7 using the other cable clamp.
8. Route the transducer cable as needed to the sonar unit. DO NOT CUT THE CABLE.
Try to avoid routing the cable with electrical wires or other sources of electrical
Wiring Harness Installation
The Fishfinder 120 comes with a wiring harness that connects the unit to power and
the transducer with one easy-to-remove connection. If it is necessary to extend the power
wires, use 22 AWG wire. DO NOT cut the transducer cable. This will void your warranty.
If your boat has an electrical system, it may be possible to wire the unit directly to an
unused holder on your current fuse block. If you are using the boat’s fuse block, remove
the in-line fuse holder supplied with the unit. You may also wire the unit direct to the
battery. CAUTION: The Fishfinder 120 input voltage is 10-18 volts DC. DO NOT
exceed this voltage as this may damage the unit and void the warranty.
Installing the Wiring Harness:
Determine the polarity of the power source using a Test Light or Volt Meter.
Install the Red (+) wire on the Positive fuse holder or battery terminal.
Install the Black (-) wire on the Negative fuse holder or battery terminal.
Install a 2 amp fuse in the fuse holder (fuse block only).
Align the notches on the cable plug and back of the unit. Insert the cable into the
connector and turn the lock ring counter-clockwise unit it stops.
Unit Care
Cleaning - Clean the unit housing using a cloth lightly dampened with a mild detergent
solution and then wipe dry. Avoid chemical cleaners and solvents that may damage plastic components. Do not apply cleaner to electrical contacts on the back of the unit.
Storage - Do not store the unit where exposure to temperature extremes may occur, as
permanent damage may result.
Drill Pilot Holes Here
Please read through these instructions thoroughly before attempting installation. Make sure
you completely understand these instructions before you begin. When in doubt, seek professional assistance. Be sure the wiring harness reaches the unit and transducer location before
beginning installation. The Garmin Fishfinder 120 hardware allows for installation on either
the transom or trolling motor. Please check the packing list below. If you are missing any items,
please contact your Garmin dealer.
Packing List:
J - 5 x 30 mm Screws (2)
1. Insert the Rubber Washer and Plastic Spacer
in the transducer at the same time. DO NOT
lubricate the Rubber Washer.
2. Route the cable towards the back and
slide the transducer into the mounting bracket.
3. Place a 5 mm Flat Washer on the 10-32 x
1.75" screw and insert the screw through
the Mounting Bracket, Spacer, and Rubber
4. Place the remaining 5 mm Flat Washer on
the exposed end and install the 10-32
Lock Nut finger tight. The transducer is
tightened further after installation on boat.
Align with transom
bottom. Transducer should
extend 1/8” below fiberglass hulls or 3/8” below
aluminum hulls.
f Transom
Bottom o
Keep Parallel With Water Line
Testing the Transom Mount Installation
This test is to be performed after the unit installation. See unit operating instructions for additional use information. Since water is necessary to carry the sonar signal,
the Fishfinder 120 does not function properly with the transducer out of the water.
When you place your boat in the water CHECK FOR LEAKS around the screw holes
that are below the water line. DO NOT leave your boat in the water for an extended
period of time without checking for leaks.
1. Begin testing the installation at a slow speed. If the sonar appears to be working
properly gradually increase the boat’s speed observing the sonar’s operation. If the
sonar signal suddenly is lost or the bottom return is severely degraded, note the
speed at which this occurs.
2. Return the boat to the speed the signal was lost. Make moderate turns in both
directions and see if the signal improves.
3. If the signal strength improves while turning, adjust the transducer so that it
extends another 1/8" below the transom of the boat. It may take several adjustments to eliminate the degradation.
4. If the signal does not improve it may be necessary to move the transducer to a
different location.
The Fishfinder 120 is able to display a variety of useful information about the
underwater environment. Below are a few things the unit helps you see.
Water Depth
The unit displays water depth and can provide a warning
when a specific depth is encountered. The Depth
Scale is displayed from top to bottom along the
right side of the display. Messages and Alarm
Icons are displayed along the bottom.
Water Temperature
The unit displays the water temperature at the
The unit displays fish as arches or fish symbols in
3 sizes and can alert you when a fish is detected.
Thermocline and Structure
GARMIN’s See-Thru® technology can display
more than just the thermocline and structure, the
(Simulated display)
unit displays fish in and below the thermocline,
trees, brush, and deadfall.
Bottom Shape and Type
Garmin’s unique DCG® (Depth Control Gain) system provides
a clear graphic representation of the bottom type and its shape.
Using the Adjustment Menu
The Adjustment Menu allows direct access to the
settings most commonly changed while using the unit.
These include the depth Range, Gain, Zoom, and the
View settings. Current Adjustment Menu settings may
be viewed by pressing the MENU key. Press MENU
again to hide the window or to exit any window. The
current adjustment option always displays in the
upper left of the display. Press LEFT or RIGHT on the
ARROW keys to scroll through the available options.
Adjustment Menu — Range
Setup Menu — Graph: Whiteline
Setup Menu — Units: Depth
Sets the display depth range. The unit can be set to automatically track the
bottom or set to a user-specified range. Available settings are: ‘Auto’ (default) and
15-600 ft.
Controls how the unit displays information about the bottom type (hard or
Choose to display measurements in Feet (ft, default), Meters (m) or Fathoms (fa). (If
soft). With Whiteline ‘Off’, the bottom return displays as solid black and contains no the ‘Depth Alarm’ is set when ‘Units’ are changed, the ‘Depth Alarm’ is defaulted to ‘Off’)
information on bottom hardness. With Whiteline ‘On’, the bottom return becomes
Setup Menu — Units: Temperature
a grayscale pattern and can be used to determine bottom hardness. A hard bottom
Fishfinder 120
The UP and DOWN ARROW keys are used to
select items on the Adjustment Menu and Setup
menu. The LEFT and RIGHT ARROW keys are
used to quickly cycle through Adjustment Menu
Operational Instructions
Thank you for choosing the Garmin Fishfinder 120. This product is designed for
easy operation and to provide years of reliable service. Please read through these instructions to get the most out of your new unit. If you encounter a problem please contact
our Product Support Department at 913-397-8200, Monday - Friday 8:00 a.m. to 5:00
p.m. CST or on the internet at
Case: Fully Gasketed, high-impact plastic alloy
Display: 3.1”H x 3.2”W (7.9 x 8.1 cm), 240 x 128 pixels
Size: 6.1” W x 4.9” H x 2.6 D (15.5 x 12.5 x 6.6 cm); Weight: 18.7 oz.
Temperature Range: +5° to 158°F (-15C to 70C)
Waterproof: IEC 529, level IPX-7 (submerged to 1 meter for 30 minutes)
Internal memory backup to retain user settings
Input: 10 to 18 Vdc w/ high voltage protection
Usage: 8 watts maximum, Nominal: 12 Vdc @ 0.5 amps
Sonar Power Output: 100 watts (RMS), 800 watts (peak to peak)
Frequency: 200kHz
Depth: 600 foot max depth (Depth capacity is dependent on water salinity, bottom type and other
The ENTER key is used to activate/deactivate
the Adjustment Menu and Setup Menu data
fields for review or changes.
The MENU key is used to activate/deactivate
Adjustment and Setup Menus.
The POWER Key is used to turn the unit on/off
and to activate the display backlight. Press and
hold to turn the unit on/off. Press briefly and
release to activate the backlight. To change the
backlight level, press the POWER key repeatedly to cycle between Off, Low and High.
water conditions.)
Specifications subject to change without notice.
Setup Menu — Alarms: Battery
Sounds an alarm when the battery is reaching a critical state of discharge.
Setup Menu — Alarms: Shallow/Deep Water Alarm
‘Shallow’ and ‘Deep’ can be set to sound a shallow/deep water warning at a depth
Adjustment Menu — Gain
determined by you. (If the either alarm is set and ‘Depth’ units are changed, both alarms
Controls the sensitivity of the unit’s sonar receiver. This provides some flexibility default to ‘Off’.) These alarms may be set to ‘Off’ (default) or from 1-600 ft.
in what is seen on the display. To see more detail, increase the receiver sensitivity by Setup Menu — Alarms: Fish Alarm
selecting a higher gain (+). If there is too much detail or if the screen is cluttered,
Sounds an alarm when the unit detects what it determines to be a fish. The alarm
lowering the sensitivity (-) may increase the clarity of the display. Available settings
selections are: ‘Off’ (default) or ‘On’.
are: ‘Normal’ ( default) and +5 to -5.
Setup Menu — Graph: Fish ID
Adjustment Menu — Scroll
Adjusts the rate that the graph scrolls from right to left. If you are sitting still or the
graph is moving too fast, slowing or pausing the graph can be beneficial.
Adjustment Menu — Zoom
Selects a display zoom scale. Available settings are: ‘OFF’ (default), ‘2X’ and ‘4X’
Adjustment Menu — View
‘View’ is available only when a Zoom scale other than ‘OFF’ is selected. This setting allows you to select a specific zoom area to view on the display or allow the unit
to automatically select a zoomed viewing area based on the bottom. When adjusting
this setting, the top and bottom numbers reflect the zoomed view depth range.
Understanding Sonar
To understand what the unit is displaying, it is important to have a general knowledge of how the unit works and how it determines what to display. The unit operates by
transmitting sound waves toward the bottom of a lake, stream, or seabed in a cone shaped
pattern. The area covered by the transmitted sound waves is determined by the cone
angle of the transducer and the water depth. Using
Garmin’s standard 20° transducer, the coverage is
approximately 1/3rd of the water depth. The coverage
area at a 30-foot depth is approximately a 10-foot
diameter circle.
When a transmitted soundwave strikes an
underwater object, sound is reflected back to the
transducer. The transducer collects the reflected sound
waves and sends the data to the unit to be processed
and displayed on the graph. The underwater data is
displayed on the graph in the order that it is returned:
first returned—first on the graph. Generally speaking,
if the only thing between the transducer and the
bottom is water, the first strong return comes from
the bottom directly below the transducer. The first
strong return sets the bottom level. Weaker secondary
returns provide the detailed data. A fish may be in the
coverage area of the transducer, but remember the first
strong return sets the bottom level. Any fish in a Dead
returns a stronger signal and displays a thicker bottom layer. A weaker (soft) bottom
return displays a thinner bottom layer. The selections are: ‘Off’ or ‘On’ (default).
Setup Menu — Graph: Noise Reject
Filters unwanted noise from the graph (especially when moving at faster speeds)
and can be turned ‘Off’ or set to a fixed value from 1-100%. Remember when setting the
‘Noise Reject’, the higher the noise rejection setting, the more likely the unit does not
Determines how the graph displays underwater targets and background informa- show fish or structure. The selections are: 1-100% (default 50%) or ‘Off’.
tion. If ‘Fish ID’ is set to ‘Off’, the unit displays all of the available information about Setup Menu — Numbers: Size
the underwater environment. If a fish symbol is selected, the graph displays only the
Displays either ‘Normal’ (default) or ‘Large’ depth, temp. and battery numbers.
information related to that symbol (large, medium and small sizes).
— All available information is displayed. (default)
— Suspended targets displayed as symbols. No background information is
displayed in this mode.
— Same as above with target depth displayed.
— Suspended targets display as symbols. In this mode background
information is still displayed making fish identification easier.
— Same as above with target depth displayed.
Zone is not detected by the sonar. The
fish is never detected since the bottom
level is never set below the fish. The
fish on the right side of the display
(shown in light grey) is detected and
displayed when the transducer cone
passes over the fish.
It is important to understand that
the unit does not display a 3-D representation of the underwater environment. The unit can display multiple
things (such as a fish and a tree) at
the same time but can not determine
where the return originated, only when
it was received. Remember that the
Fishfinder displays a 2-D picture of the
underwater environment. A fish and an
underwater structure could be located
anywhere in the coverage area at that
slice of time.
Dead Zone
Warning: This product, its packaging, and its components contain chemicals known to the State
of California to cause cancer, birth defects, or reproductive harm. This Notice is being provided
in accordance with California’s Proposition 65. If you have any questions or would like additional
information, please refer to our web site at
Setup Menu — Numbers: Battery
Choose to either ‘Hide’ (default) or ‘Show’ the current battery voltage.
Setup Menu — Numbers: Water Temp.
‘Water Temp’ automatically displays when set to ‘Auto’ (default) or you may choose
to ‘Hide’ the temperature numbers. Water temperature will only display if you have a
temperature capable transducer.
To immediately change the current adjustment option, press the UP or DOWN
ARROW key. If you wish to review the available settings before making a change,
press the ENTER key to activate the adjustment window.
To change a setting on the unit:
1. Press MENU, then using the UP or DOWN ARROW key, move the selection arrow
to the desired option and press ENTER. Choose ‘Setup’ for the main Setup Menu.
2. Using the UP or DOWN ARROW key move the selection arrow to the desired
setting and press ENTER. (The selection arrow wraps when you reach the end of
a menu and adjustment window. If holding the ARROW key down, release then
press.) Holding down on an ARROW key rapidly advances the selection speed.
3. To close a setting or menu window, press MENU.
Choose to display the water temperature in Fahrenheit (°F, default) or Celsius (°C)
Setup Menu — System: Simulator
The Fishfinder 120 comes with a built-in simulator mode that allows you to
practice and learn the operation of the unit at home rather than on the water. The
unit indicates that it is running the simulator mode by displaying a message in the
lower left of the display. While in the simulator mode, the unit displays a random
bottom scene and the Fishfinder 120 can be controlled (except Noise Reject and
Gain) just as if it were on the water. To exit the Simulator, turn the unit off. If no
keys are pressed for 2 minutes, the unit automatically resets to default unit settings
while in simulator mode. If the unit does not detect a transducer attached, it automatically starts in Simulator mode.
Setup Menu — System: Contrast
Adjusts to compensate for different light levels or viewing angles.
Setup Menu — System: Defaults
This option allows you to restore the factory default settings for the unit.
Limited Warranty
Software License Agreement
This Garmin product is warranted to be free from defects in materials or workmanship for one year from
the date of purchase. Within this period, Garmin will at its sole option, repair or replace any components
that fail in normal use. Such repairs or replacement will be made at no charge to the customer for parts or
labor, provided that the customer shall be responsible for any transportation cost. This warranty does not
cover failures due to abuse, misuse, accident or unauthorized alteration or repairs.
THIS PRODUCT OR FROM DEFECTS IN THE PRODUCT. Some states do not allow the exclusion of
incidental or consequential damages, so the above limitations may not apply to you.
Garmin retains the exclusive right to repair or replace the unit or software or offer a full refund of the
purchase price at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE REMEDY
FOR ANY BREACH OF WARRANTY. Products sold through online auctions are not eligible for rebates or
other special offers from Garmin. Online auction confirmations are not accepted for warranty verification.
To obtain warranty service, an original or copy of the sales receipt from the original retailer is required.
Garmin will not replace missing components from any package purchased through an online auction.
To obtain warranty service, contact your local Garmin authorized dealer. Or call Garmin Customer
Service for shipping instructions and a RMA tracking number. The unit should be securely packed with
the tracking number clearly written on the outside of the package. The unit should then be sent, freight
charges prepaid, to any Garmin warranty service station. A copy of the original sales receipt is required as
the proof of purchase for warranty repairs.
The Fishfinder 120 has no user-serviceable parts and is fastened shut with screws. Any attempt to open
the case to change or modify the unit in any way will void your warranty and may result in permanent
damage to the equipment.
By using the Fishfinder 120, you agree to be bound by the terms and conditions of the following software license agreement. Please read this agreement carefully.
Garmin grants you a limited license to use the software embedded in this device (the “Software”) in
binary executable form in the normal operation of the product. Title, ownership rights and intellectual
property rights in and to the Software remain in Garmin.
You acknowledge that the Software is the property of Garmin and is protected under the United States of
America copyright laws and international copyright treaties. You further acknowledge that the structure,
organization and code of the Software are valuable trade secrets of Garmin and that the Software in
source code form remains a valuable trade secret of Garmin. You agree not to decompile, disassemble,
modify, reverse assemble, reverse engineer or reduce to human readable form the Software or any part
thereof or create any derivative works based on the Software. You agree not to export or re-export the
Software to any country in violation of the export control laws of the United States of America.
© Copyright 2003 Garmin LTD. or its subsidiaries
GARMIN®, DCG® and See-Thru® are registered trademarks of Garmin Ltd. or its subsidiaries
and may not be used without the express permission of GARMIN.
Garmin International, Inc. 1200 East 151st Street, Olathe, Kansas 66062, U.S.A.
Tel.913/397.8200 Fax. 913/397.8282
Garmin (Europe) Ltd. Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51
9DL, U.K. Tel. 44/1794.519944 Fax.44/1794.519222
Garmin Corporation No. 68, Jangshu 2nd Road, Shijr, Taipei County, Taiwan
Tel. 886/2.2642.9199 Fax. 886/2.2642.9099
Part Number 190-00306-00 Rev. A