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OWNERS MANUAL
AND REFERENCE
GPSMAP 235
SounderTM
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Software Version 4.01 or above
Internal Database Version 3.00   © GARMIN Corporation
G-chartTM cartridge  data  is  copyrighted  by  Navionics  Corporation  and  GARMIN
Corporation  and  may  not  be  copied  or  used  for  any  other  purpose  without 
permission.
© 1999 GARMIN Corporation
GARMIN International, Inc.
1200 E. 151st Street, Olathe, KS 66062, USA
Tel: 913.397.8200 or 1.800.800.1020
Website: www.garmin.com
Fax: 913.397.8282
GARMIN (Europe) Ltd.
Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9AQ, UK
Tel: 011.44.1794.519944
Fax: 011.44.1794.519222
GARMIN (Asia) Corp.
3th Fl, No. 1, Lane 45, Pao-Hsing Road, Hsin-Tien, Taipei,Taiwan R.O.C.
Fax: 011.886. 02.2917.1758
Tel: 011.886.02.2917.4107
All  rights  reserved.  No  part  of  this  manual  may  be  reproduced  or  transmitted  in  any
form or by any means, electronic or manual, including photocopying and recording, for
any purpose without the express written permission of GARMIN.
Information in this document is subject to change without notice. GARMIN reserves the
right to change or improve its products and to make changes in the content without oblig-
ation to notify any person or organization of such changes or improvements.
October 1999
Part #190-00138-10 Rev.B                     Printed in Taiwan
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Warning
The  GPSMAP  235  Sounder  should  not  be  used  as  a  navigational  aid  or  depth  sounder  to 
prevent collision, grounding, or boat damage, any of which could result in personal injury.
For reasons of safety, we also recommend that you operate your boat at very slow speed if
you suspect shallow water or submerged objects.
INTRODUCTION
Warning
GARMIN, GPSMAP, G-chart, AutoLocate,
TracBack and PhaseTrac12 are trademarks of
GARMIN Corporation and may only be used
with permission. All rights are reserved.
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INTRODUCTION
Cautions
CAUTION!
The GARMIN GPSMAP 235 Sounder has no
user-serviceable  parts.  Should  you  ever
encounter a problem with your unit, please take
it to an authorized GARMIN dealer for repairs.
Any attempt to open the case to change or mod-
ify the unit in any way will void your warranty
and may result in permanent damage to the
equipment.
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Caution
The  GPS  system  is  operated  by  the  United  States  government,  which  is  solely
responsible  for  its  accuracy  and  maintenance.  The  system  is  subject  to  changes
which  could  affect  the  accuracy  and  performance  of  all  GPS  equipment.  Although
the  GARMIN GPSMAP  235  Sounder  is  a  precision  electronic  NAVigation  AID
(NAVAID), any NAVAID can be misused or misinterpreted and, therefore, become
unsafe. 
Use  the  GPSMAP  235  Sounder  at  your  own  risk.  To  reduce  the  risk  of  unsafe
operation, carefully review and understand all aspects of this Owner’s Manual—and
thoroughly practice operation using the simulator mode prior to actual use. When in
actual use, carefully compare indications from the GPSMAP 235 Sounder to all avail-
able  navigation  sources,  including  the  information  from  other  NAVAIDs,  visual
sightings, charts, etc. For safety, always resolve any discrepancies before continuing
navigation.
NOTE: The GPSMAP 235 Sounder generates, uses, and can radiate radio frequen-
cy  energy  and,  if  not  installed  and  used  in  accordance  with  the  instructions,  may
cause  harmful  interference  to  radio  communications.  There  is  no  guarantee  that
interference  will  not  occur  in  a  particular  installation.  If  the  sounder  does  cause
harmful interference, the user is encouraged to try to correct the interference by relo-
cating the equipment or connecting the equipment to a different circuit. Consult an
authorized dealer or other qualified technician for additional help if these remedies
do not correct the problem.
The  GPSMAP 235  Sounder  complies  with  Part  15  of  the  FCC  limits  for  class  B
digital  devices.  Operation  is  subject  to  the  following  conditions:  (1)  The  sounder
may not cause harmful interference, and (2) the sounder must accept any interfer-
ence received, including interference that may cause undesired operation.
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Designed for detailed electronic charting and complete depth sounding capabil-
ity, the GARMIN GPSMAP 235 Sounder is a powerful navigation device that also
gives you the fishfinding information you need in fresh or saltwater.
Precision Performance:
• High-contrast, four-level gray, LCD screen
• 12  channel  receiver  tracks  and  uses  up  to  12  satellites  simultaneously 
for fast, accurate positioning
• Differential-Ready— just add the optional GBR 21 beacon receiver for better
than 5-meter accuracy
Advanced Navigating and Plotting:
• 250 alphanumeric waypoints with selectable icons and comments
• Built-in database usable from 4096 to 64 nm worldwide and to 32 nm in the
continental United States.
• 20 reversible routes with up to 30 waypoints each
• G-chartTM electronic charting with inland and offshore coverage
• LORAN TD to GPS Lat/Lon Coordinate conversion
Superior Fishfinding Ability:
• Four zoom levels with a moving view window
• Underwater waypoint marking
• Map/Sounder split screen displays navigation and fishfinding information
• Fish and depth alarms
• Digital depth continuously displayed on all pages
• Dual frequency operation for maximum coverage with good bottom detail
• Efficient noise rejection circuitry for removing cross talk and noise
INTRODUCTION
Sounder Capabilities
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INTRODUCTION
Warranty
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Limited Warranty
GARMIN warrants this product to be free from defects in materials and manu-
facture for one year from the date of purchase. GARMIN will, at its sole option,
repair or replace any components which fail in normal use. Such repairs or replace-
ment will be made at no charge to the customer for parts or labor. The customer is,
however, responsible for any transportation costs. This warranty does not cover fail-
ures due to abuse, misuse, accident or unauthorized alteration or repairs.
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE EXCULSIVE
AND IN LIEU OF ALL OTHER WARRANTIES EXPRESSED, IMPLIED, OR STATU-
TORY, INCLUDING ANY LIABILITY ARISING UNDER WARRANTY OF MER-
CHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, STATUTORY OR
OTHTERWISE. THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS,
WHICH MAY VARY FROM STATE TO STATE.
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPE-
CIAL, INDIRECT OR CONSEQUENTIAL DAMAGES, WHETHER RESULTING
FROM THE USE, MISUSE, OR INABILITY TO USE, MISUSE, OR INABILITY TO
USE 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.
To obtain warranty service, call the GARMIN Customer Service Department
(913.397.8200) for a returned merchandise tracking number. The unit should be
securely packaged with the tracking number clearly marked on the outside of the
package and sent freight prepaid and insured to a GARMIN warranty service station.
A copy of the original sales receipt is required as the proof of purchase for warranty
repairs. GARMIN retains the exclusive right to repair or replace the unit or software
at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE
REMEDY FOR ANY BREACH OF WARRANTY.
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Preface
INTRODUCTION
Preface
Congratulations  on  choosing  one  of  the  most  advanced  depth  sounding  and
marine  navigation  systems  available.  The  GARMIN GPSMAP  235  Sounder  com-
bines  the  proven  performance  of  GARMIN  GPS,  powerful  G-Chart  electronic
charting, and full featured depth sounding into one unit to create an unsurpassed
marine navigation and fishfinding package.
To get the most out of your new navigation and sounding system, take the time
to go through this operator’s manual and learn the operating procedures for your
unit. This manual is broken down into two parts for your convenience.
Part One introduces you to the GPSMAP 235 Sounder and provides a “getting
started tour” so that you may become more familiar with the unit. This section will
provide you with a basic working knowledge of the sounder.
Part  Two is  divided  into  sections  that  provide  detailed  references  to  the
advanced features and operations of the GPSMAP 235 Sounder. Part two allows
you to concentrate on a specific topic quickly, without reading through entire por-
tions of text that you may not need. This section can be used to look up detailed
information about the GPSMAP 235 Sounder.
WARNING!
The electronic chart is an aid to navigation and is
designed to augment the use of authorized govern-
ment charts, not replace them. Only official gov-
ernment charts and notices to mariners contain
all information needed for safe navigation— and,
as always, the user is responsible for their 
prudent use.
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INTRODUCTION
Packing List
Before  installing  and  using  with  your  sounder,  please  check  to  see  that  your
package includes the following items. If any parts are missing, please contact your
GARMIN dealer immediately.
*Standard Package:
• GPSMAP 235 Sounder
• External GPS Antenna and 30’ cable
• Power/Data Cable
• Mounting and Gimbal Bracket
• Owner’s Manual
• Quick Reference Card
*For assembly part number 010-00119-01, a transom mount transducer is included.
Optional Accessories:
• G-chart Electronic Chart Cartridges
• PC Kit 
• In-Hull  and  Transom-Mount  Transducers  with  or  without  temperature  and
speed-through-water capability.
• Additional mounting brackets and cables.
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