Humminbird 1158c Combo Installation And Operation Manual page 43

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.
Using the Mounting Bracket to
Mark the Initial Drill Holes
Fourth Hole
Mark Initial Drill Holes
Positioning the
Mounting Bracket
Level
3. Continue to hold the bracket on the transom of the boat,
and use a pencil or marker to mark where to drill the two
mounting holes. Mark the drill holes near the top of each
slot, making sure that your mark is centered in the slot.
NOTE: The third hole should not be drilled until the angle and
height of the transducer is finalized, which you will not do until
a later procedure.
4. Make sure that the drill bit is perpendicular to the actual
surface of the transom, NOT parallel to the ground, before
you drill. Using a 5/32" bit, drill the two holes only to a
Third Hole
depth of approximately 1".
NOTE: On fiberglass hulls, it is best to use progressively larger drill bits
to reduce the chance of chipping or flaking the outer coating.
Boat Hull Types Require
Different Mounting Positions
1/4" for fiberglass
1/8" for aluminum
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Transom Mount - DualBeam™ PLUS