Regal 3300 Owner's Manual page 171

The depth finder will display depths of 2-199 feet, 1-92 meters, or 1-54
fathoms. To accommodate greater depths to be displayed in the "ft"
feet mode the depth sounder will automatically change to "F" fathoms
mode and continue to display depths to around 54 fathoms.
When the depth decreases below 200 feet the display will return to the
"ft" mode. Limits on depth will vary depending on transducers and
bottom conditions.
If the reading is less than 19.9 feet, meters, or fathoms, 1/10th
increments will be displayed. If the reading is more than 19.9 feet, all
readings will be in whole numbers.
The depth finder features an audible and LCD displayed depth alarm
with adjustable shallow and deep limits and a depth below keel offset
feature. These settings once made are stored in memory and will remain
even if the battery is not connected. Store vessel with bow slightly
tilted for proper drainage.
Typical
Transducer
Refer to the equipment manufacturer's manual for additional
information.
https://www.boat-manuals.com/
Features
NOTT: Near the keel (center
of boat bottom) the depth
sounder transducer is
l o c a te d . I t b o u n c e s a
constant signal off the
bottom and sends it to the
dash head unit. Never use
bottom paint on the hull
side of the transducer
since it will effect the unit's
operation.
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