Depth Finder

Having an accurate depth finder is almost mandatory if you are using a boat and motor with a propellor.  Even better, a combination unit that has GPS / Sonar (depth finder or fish finder) will help you immensely.   Using these tools will help you avoid hazards that cannot be seen above water, help you locate structure beneath the surface, and will help you find certain depths where you have caught fish earlier, or the fishing report tells you at which depth fish are being caught.

Depth Finder - Components

Garmin 010-01804-01 Echomap Chirp 93SV with transducer
Garmin 010-01804-01 Echomap Chirp 93SV with transducer
The Head unit is what most people think of when they think Depth Finder / Fish Finder or a combination GPS unit. Also needed is a transducer- that gets placed on the rear of your boat that sends a signal to through the water to ping the bottom and also identify anything that is in the water between the boat and the water. You can buy a unit that will record a downview, side view and/or standard sonar cone. The Garmin unit above has most of the features mentioned here. High definition display, built in maps - you should check this one out.

Most newer units have the GPS antenna built into the head unit. Older models come with an external antenna that will need to be mounted somewhere on your vehicle.  Most units now measure speed through GPS, as well as the time of day.  

Features and Options

Speed, power, color and clarity can be very different between different models.  Depending on your application, you will want to choose the unit that will best suit your needs.  Many older units are still working and black and white.  If they work, great.  When ready to update your unit check out the three newer units below.  Of course color is pretty standard and the resolution, like the TV market has gone HD.  This means that the clarity of the underwater world that gets transmitted will be just that much better on your monitor. 

Also varying is the speed of these units.  How fast and how many directions will the pings leave the transducer.  Some newer units also feature a mapping feature, which means that you can fill in depth contours that may not be as accurate as they will be after turning on this feature.  Yes, this is true.

Side Imaging

This new feature - which gives you the ability to see structure not just below the boat, but actually on each side in much detail.    Seeing is believing, but this feature can identify a foundation, bridge, tree etc like never before.  All this means that you can learn the structure in great detail like never before.

Lowrance HDS-9 Gen3 Fishfinder with Insight USA and 83/200 LSS-2 Transducer. Gen3 now comes equipped with CHIRP technology, giving you a clearer picture and a greater chance of locating the fish you want. You're able to view CHIRP sonar and StructureScan 3D, live, at the same time, giving you a greater view of both fish and structures below and on either side of your boat. Access your information faster with either the touchscreen or the keypad for incredibly fast access to all of your HDS features.  Brilliant Display: Touchscreen interface puts a wealth of GPS chartplotting, navigation and more right at your fingertips; 9" 800 x 480 16-bit color TFT LCD display for surprisingly crisp, clear views all hours of the day, even in bright sunlight and wide angles... and much more. Click on the links above and read more.

Down Imaging

Another great feature which means like never before you can differentiate more clearly what lies below your boat as you pass over.  You can better distinguish between fish, brush, rock and bait.  

Humminbird HELIX 9 DI GPS | HELIX 9 Series | 409930-1. If you've got room on your dash or bow for a larger format display, start with the full-featured HELIX 9 Series. View Sonar images and charts side-by-side with a full range of technology options. The HELIX 9 DI GPS features a brilliant 480V x 800H, 9" color display with backlight. Down Imaging and Dual Beam PLUS Sonar with 4000 watts PTP power output, Precision Internal GPS Chart plotting with built-in Humminbird ContourXD map and Ethernet networking capabilities.


On larger lakes, and certainly on bodies of water you are not familiar with, GPS is a very important safety feature.  It can also mean you can find your way back to where you started with ease. Many units today also offer the ability to have bottom topography and contours loaded into the unit so that its GPS will track where you are on the water in relation to the specific lake map.  Whether fishing a lake for the first time or for the 100th time, this offers you the ability to travel great distances safely, and return to your favorite fishing spot time after time with the waypoint feature.  You are able to mark on your map and save it into memory specific spots where you want to return.

Following in the success of the echomap CHIRP Combo Series, Garmin is proud to announce the new echomap CHIRP combos with Clearly Scanning sonar technology. The CV Series offers Built-in CHIRP traditional sonar and CHIRP Clearly. The SV Series gives you Built-in CHIRP traditional sonar, CHIRP clearer and CHIRP sidevü capabilities. Each display size for the echomap combos is offered with either U.S. Bluechart G2 charts, U.S. Lakevü HD maps, Canada lakevü HD maps or a worldwide basemap. New Garmin QuickDraw contours software feature lets you create your own maps, with up to 1-foot contour lines, on any body of water.

Make Unit Portable

Humminbird 898 Transducer Transom Mount and Transducer

There are available portable depth finders.  These are helpful if you want to fish in a rented boat, ice fish, or don't want to permanently mount your depth finder on your boat.   With a bit of creativity and the purchase of 2-3 additional items you can make your own combo unit portable.  This unit below has been used on rental boats in Canada for the past several years.  The items used include the following:

  • Johnny Ray Snap Dash Mount
  • Additional Humminbird Transducer
  • Portable Transom Mount for Transducers
  • Clamp - used to secure my Humminbird/GPS antenna to the side of the boat
A small platform from scrap HDPE on which to mount the snap on dash mount, the clamp, and the GPS Antenna. Of course, aluminum or stainless steel hardware - nuts and bolts were used.. When transfering your gps/depth finder from place to place use caution not to drop your unit - they are sensitive. Here are pictures of the finished project.
Humminbird 898c SI Portable Depth FinderOf course, newer units have build in GPS antennas.