Lowrance PRO X51 Installation And Operation Instructions Manual page 11

Mark the center of each slot for the mounting screw pilot holes. You
will drill one hole in the center of each slot.
Drill the holes using the #29 bit (for the #10 screws).
Transom
Position transducer mount on transom and mark mounting holes.
Side view shown at left and seen from above at right.
5. Attaching transducer to transom. Remove the transducer from
the bracket and re-assemble it with the cable passing through the
bracket over the bolt as shown in the following figures.
Route cable over bolt and through bracket. Side view shown at left and
Attach the transducer to the transom. Slide the transducer up or
down until it's aligned properly with the bottom of the hull as shown
in the preceding and following figures. Tighten the bracket's
mounting screws, sealing them with the sealant/adhesive compound.
Adjust the transducer so that it's parallel to the ground and tighten
the nut until it touches the outer washer, then add 1/4 turn. Don't
over tighten the lock nut! If you do, the transducer won't "kick-up" if
it strikes an object in the water.
Transom
seen from above at right.
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