I've never used an Echopilot, but after 16 years of using a Interphase "Probe" FLS I still find it generally useful, and in some circumstances a lifesaver. Obviously, my examples are not the latest models, and perhaps some of the downsides may have been improved.
They do give a good idea of the general shape of the bottom ahead of the boat. The distance ahead that is viewed is dependent upon the depth and the quality of the bottom, but averages around 3-4 times the depth. This is extremely helpful when entering poorly charted anchorages
, especially in poor visibility.
In some situations, ie coral
lagoons, where the general depths are large (100-200 feet), one can see a coral head
or other isolated rock at distances of >500 feet.
A floating semi-submerged container would indeed be visible at a useful distance IF you were watching the screen
at the right time... logs are less likely due to their smaller depth below the surface clutter. See comment below about alarms.
Not so good things:
Because of the physics of sound propagation, the further ahead one is looking, the slower the sweep must go. Thus, at maximum range (1200 feet) on the fastest setting it takes around 15 seconds (this is from memory... may be longer) to sweep from straight ahead to straight down. This means that it is possible that a poor target on the surface would not be observed at a useful distance especially if one is going fast.
Further, the beam width is +/- 12 degrees. If the boat is yawing much it is possible to miss a narrow bommie or floating hazard.
In general, the display requires some practice to interpret correctly, much like radar
The alarms, while useful on paper, have not proven even usable in our experience. They are set to trip on any return signal within the designated depth range, and if one sets the sensitivity high enough to respond to hazards there are constant false alarms from noise
, surface clutter etc. Thus one must actually be watching the screen continually if avoiding floating logs or containers is your goal. Not gonna happen on our boat!
So, it isn't quite as good as the glossy adverts promise, but for those of us who frequently ply poorly charted waters or like to explore in coral areas, I think it is an essential tool.