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SECTION TWO Installing the transducer
Choose the mounting
location to obtain the best
possible performance from
the transducer and the 490.
Take into account the
vessel's maximum speed
when selecting a mounting
location, as turbulence can
affect echo sounding
capabilities.
Page 8
The two most common problems with echo sounder
installations stem from noise and cavitation. Either of these
situations can produce poor performance.
Noise occurs when the transducer cable is routed too closely to
noise-producing electronics, such as alternators, AC generators,
radars, etc. To avoid problems with noise, route the transducer
cable by itself (not in a bundle) and away from other wires or
cables and the engine.
Cavitation is similar to hydroplaning. In some cases, air bubbles
will come between the transducer and the water. When this
happens, the transducer can't get its energy into the water
properly, and won't be able to detect any echoes. To avoid
cavitation, choose a mounting location with good water flow all
around it at all speeds.
Before any drilling or cutting takes place, carefully choose a
mounting location for the transducer that meets the following
criteria (also see Figure 1 on page 9), depending on the type of
vessel:
•
the transducer and its cable are as far as possible from
other electrical cables
•
leaves room above the transducer for the transducer's
stem, housing, and cable
•
the path for running the transducer's cable is reasonably
direct—keep in mind that the transducer cable is 33 feet
long (10 meters). To prevent damage, coil any excess cable
and secure it
•
water turbulence and noise are minimal, decreasing the
amount of bubbles passing over the transducer face
•
the transducer isn't behind hull irregularities or near
eroding paint; both indicate areas subject to turbulence
•
the transducer is as far as possible from the engine or
propellers, and inboard of the lifting strakes
•
the transducer always remains submerged and
perpendicular to the waterline
•
the transducer is easily accessible from inside the vessel
for adjustments and maintenance
•
the transducer's ultrasonic beams aren't obstructed by the
keel, propeller shafts, or any other part of the vessel
•
the transducer is parallel with the water surface
•
the hull thickness falls within the limits in Table 2 below
(all dimensions are perpendicular to the waterline):
490 INSTALLATION MANUAL, Revision B2
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