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Chapter 2: Installation 19
Marking and Hole Drilling
1. At the selected location on the starboard side of the hull, position the
transducer, so the transducer projects 3mm (1/8") below the bottom edge
of the transom (see Figure 2-10 ).
2. Being sure the bottom of the transducer is parallel to the waterline, mark
the location of the screw holes with an “X” in the center of the two outer
most slots.
CAUTION: Always wear safety goggles and a dust mask.
3. Using a 4mm, #23, or 9/64" drill bit, drill two holes 22mm (7/8") deep at
the locations indicated. To prevent drilling too deeply, wrap masking tape
around the bit 22mm (7/8") from the point.
Fiberglass hull—Minimize surface cracking by chamfering the gelcoat.
If a chamfer bit or countersink bit is not available, start drilling with a
6mm or 1/4" bit to a depth of 1mm (1/16").
Plastic Shim
• Standard transom (13° transom angle)—The bracket is designed for a
standard 13° transom angle. The shim is not needed for this installation.
Skip to Mounting the Bracket.
• Stepped transom and jet boats (3° transom angle) —Use the shim with
the tapered end down. Be sure the nuts are in the slots in the back of the
bracket before applying the shim (see Figure 2-8 ).
• Small aluminum and fiberglass boats (20° transom angle)—Use the
shim with the tapered end up. Be sure the nuts are in the slots in the back
of the bracket before applying the shim (see Figure 2-8 ).
• If you are unsure about using the shim, do one of the following:
• Measure the transom angle of your boat using a digital level or bubble
level and protractor. Then follow the instructions above for your tran-
som angle.
• Experiment with the shim by following the instructions Mounting
the Bracket and Checking the Angle and Projection.
Mounting the Bracket
1. Apply marine sealant to the threads of two, #10 x 1-3/4", self-tapping
bracket screws to prevent water seepage into the transom.
2. Screw the transducer (with the shim if needed) to the hull (see Figure 2-10
). Do not tighten the screws at this time.