Humminbird 998c SI - Manual (Page 25)

15 Transom Mount - DualBeam PLUS™
• If the transom is behind the propeller(s), it may be impossible to find
an area clear from turbulence, and a different mounting technique or
transducer type should be considered, such as an Inside the Hull
Transducer (see Inside the Hull Transducer Installation).
• If you plan to trailer your boat, do not mount the transducer too close
to trailer bunks or rollers to avoid moving or damaging the transducer
during loading and unloading of the boat.
• If high speed operation is critical, you may want to consider using an
In-Hull transducer instead of this Transom Mount transducer.
NOTE: The hydrodynamic shape of your transducer allows it to point straight down
without deadrise adjustment.
NOTE: If you cannot find a transom mount location that will work for your high-
speed application, find an In-Hull Transducer by contacting our Customer Resource
Center at either 1-800-633-1468 or by visiting our web site at humminbird.com.
2. Preparing the Mounting Location
In this procedure, you will determine the mounting location and drill two
mounting holes, using the transducer mounting bracket as a guide.
1. Make sure that the boat is level on the trailer, both from port to
starboard and from bow to stern, by placing your level on the deck of
the boat, first in one direction, then in the other.
2. Hold the mounting bracket against the transom of the boat in the
location you have selected. Align the bracket horizontally, using the
level; make sure that the lower corner of the bracket does not
protrude past the bottom of the hull, and there is at least 1/4"
clearance between the bottom of the bracket and the bottom of the
transom for fiberglass boats, and 1/8" clearance for aluminum
boats.
NOTE: If you have a flat-bottomed aluminum boat, some additional adjustment
may be needed to accommodate the rivets on the bottom of the boat (i.e. the gap
may need to be a little smaller than 1/8"). This will help you to avoid excessive
turbulence at high speeds.
NOTE: If your propeller moves clockwise (in forward, as you're facing the stern of
the boat from behind), mount the transducer on the starboard side, and align the
bottom right corner of the mounting bracket with the bottom of the boat. If your
propeller moves counter-clockwise (in forward, as you're facing the stern of the
boat from behind), mount the transducer on the port side, and align the bottom
left corner of the mounting bracket with the bottom of the boat.
Positioning the
Mounting Bracket
Level
Le
ve
l
Boat Hull Types Require
Different Mounting Positions
1/4” for fiberglass
1/8” for aluminum