Stay Safe with a Depth Sounder

The Raymarine i40 i40 Depth Instrument comes complete with a thru-hull transducer.
The Raymarine i40 i40 Depth Instrument comes complete with a thru-hull transducer.

A critically important piece of equipment for all vessels, both coastal and offshore is a depth sounder. On many boats, standing watch today means shifting effortlessly through full-color screens showing GPS mapping, depth sounder/fish finder, anemometer, radar and other features through an NMEA 0183, NMEA 2000 or open source network.

However, sailors who depend on paper charts and minimal electronics—VHF radio, handheld GPS and a stand-alone depth sounder—are still making successful ocean passages, blissfully innocent of the compulsion, or ability, to spend a fortune on more elaborate systems.

Just to refresh our memories, 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. That’s it.

In the $100 to $300 range, Raymarine, Faria, Nocross 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 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, thru-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 among depth sounders 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 Saltaire has served for over 20 years, including a circumnavigation, and has been in the shop only once for a rebuild of the gauge.

The choice to purchase and install a traditional, stand-alone depth sounder will depend on the specific needs of crew and vessel. Discussions regarding depth sounders, aside from fish finders, always 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.

By Bill Morris