capabilities, enabling you to see what’s underwa-
ter ahead, or to port and starboard.
As the ping, or sound wave, is transmitted
into the water by the transducer, it forms a cone-
shaped beam, which can be as narrow as 15
degrees or as wide as about 45 degrees (as shown
in the illustration on page 157). Some of the
more sophisticated units, such as those available
from Interphase Technologies (www.interphase-
tech.com), can scan through even wider arcs.
In order to receive the echo, the transducer
must be oriented correctly on the hull accord-
ing to the manufacturer’s guidelines. Most
often, some sort of fairing block is needed to
aim the beam correctly.Mounting a Transducer
To make the most of your depth sounder/
fishfinder, the transducer must be mounted in
the best location for your boat (i.e., sail or158 marine electronics installation and troubleshooting
power). We’ll cover general guidelines first, then
go into some specifics.- As much as possible, mount the trans-
ducer so it has an unobstructed path for
the beam. - Mount the transducer so it will be sub-
merged at all times while underway. This
means powerboat owners must take the
location into account when the boat is up
on plane. - Do not mount a transducer in the flow of
turbulent water, such as near a prop or
behind a strake or through-hull flange.
For inboard boats, do not mount it near
the propeller shaft struts or raw-water
intake fittings.
paddle wheelA typical transducer installed on a fairing block on a
powerboat. The joint between the transducer and the fair-
ing block is difficult to see because antifouling paint has
filled the seam, but the fairing block represents about
50% of the profile surface. This particular transducer also
includes a small paddle wheel that drives a knotmeter
function on the same instrument.Installation of a transducer. Note the fairing blocks both
inside and outside to create a level mounting surface and
(if this were a through-hull or seacock) spread any acci-
dental load (e.g., being hit by gear or trodden on). Note
also the generous amounts of bedding compound.
(Reprinted with permission from Nigel Calder’s Cruising
Handbookby Nigel Calder)fairing blockfairing block