Cruising along the Southern California coast is made much safer with a depth sounder to keep us safe from running aground, but also more enjoyable with a fish finder, which alerts us of potential dinner targets. Fortunately, there are small, easily installed units that act as both fish finder and depth sounder, which use sound waves to generate visuals of what lies below our boats.
Depth Sounders
First, let us imagine a situation where we are only a few hundred yards from the rocks along the north side of Catalina Island. We see something on shore, perhaps a school of dolphins playing or an interesting formation in the rocks that attracts our attention. As we dare to move in a bit closer, we see sharp, giant rocks appear below our hull and we throw the transmission into reverse to pull away from the submerged obstacles, perhaps even scratching the bottom of the hull in our panic.
Fiberglass hulls on small coastal boats can be as thin as ¼ inch and when we consider how much weight is pushing down on the hull, we realize a sharp boulder can cut through a thin hull like a filet knife through a yellowtail. Hence the need for a depth sounder on our boats.
In brief, a traditional depth sounder consists of a transducer mounted either on the transom or inside the hull near the keel, an analog needle gauge or digital number screen, a cord to connect the two components and two wires to the electrical panel. There are still several high-quality, stand-alone depth sounders on the market, and even if you do opt for a combination sounder/fish finder, having a back-up unit for extra safety is always a good idea.
In the $100 to $300 range, Raymarine, Faria, NorCross and Lowrance offer dependable, traditional depth sounders that are easy to install and use. They all feature weather-resistant digital LCD screens, which you may mount on a bulkhead or other exterior surface for easy viewing.
The Raymarine i40 Depth Instrument is a popular option for smaller vessels lacking a fully networked instrument array. The stand-alone kit includes a dedicated, IPX6 waterproof instrument screen, through-hull transducer, along with power and interface cables with SeaTalk data interface. Priced at roughly $300, the Raymarine i40 is a rugged, dependable instrument that will serve well on any yacht.
Faria offers a plastic through-hull transducer, which reads up to 54 fathoms (312 feet), but the unit is priced low enough for budget-minded coastal cruisers to enjoy an extra measure of safety. Another inexpensive, entry-level sounder is NorCross Marine’s Hawkeye 1B, available with either a transom-mount or hull-mount plastic transducer. The Hawkeye features an upper and lower depth alarm system consisting of an audible alarm, a red LED and an LCD message.
Signet’s SL172 is a classic with its black, round bezel and simple design, which match the analog SL254 Wind Indicator, SL11 Knotmeter and other devices in this series. The SL172 detects up to 200 feet depth and is available with either a plastic mushroom or bronze wedge transducer. The SL172 with plastic through-hull transducer on my 1966 Cal 30 Saltaire has served for over 20 years, including a circumnavigation, and has been in the shop only once for a rebuild of the monitor.
Depth Sounder/Fish Finder Combos
Combined units with both depth sounder and fish finder capability make a lot of sense, especially if we have limited space for overlapping electronics and displays. If you already have a chartplotter mounted near the helm, chances are you have the option of adding a depth transducer to the bottom of the hull and running the provided cable to the chartplotter. Garmin, Raymarine, Lowrance, Furuno and other marine electronics manufacturers offer installation kits that include through-hull depth sounders.
The other option, especially popular on small power boats, is a transducer mounted to the transom, eliminating the need to cut through the bottom of the hull. Simply screw the unit to the bottom of the transom, adding waterproof sealant to prevent water ingress, run the power wires to the battery and the cable to your chartplotter, and your depth sounder/fish finder is ready to go.
The Lowrance Eagle 5 sounder/fishfinder combo comes complete with chartplotter display unit, external transducer, C-Map charts, hardware and cables and is available for under $400. If you own a larger yacht and desire a permanent thru-hull transducer, consider a higher-end unit, such as the Simrad NSSevo3S chartplotter, which includes detailed bottom imaging, vector navigation charts and 1kW CHIRP-enabled sonar. This level of technology permits you to study not only fish passing under your hull, but also the finer details of bottom structure, including rocks, seaweed and sunken vessels.
If all you need is an inexpensive fish finder for your skiff or canoe, consider a wireless device like the Erchang F13 wireless fishfinder, which comes with a floating sensor and digital handheld monitor, or their F12 model, which looks like a flashlight you stick in the water while viewing the fish on a small digital display. Both of these are available for under $100, affordable for even the humblest of anglers.
The choice to purchase and install a traditional, stand-alone depth sounder or a modern sounder/fish finder will depend on the specific needs of crew and vessel. Discussions regarding depth sounders, aside from fish finders, usually revolve around submerged dangers. While underway on open ocean, you can generally rely on your charts for depth. But what about anchoring?
When I’m looking for my ideal anchoring depth of 20 to 40 feet, my eyes are fixed on the depth sounder, not the chart. If you can measure reliably up to 200 feet, then you can scout around a harbor for a spot to drop the hook for the night. Determine what you actually need in a depth sounder, or fish finder if that is your preference, and choose accordingly.
