Garmin 400C Owner's Manual page 13

When selecting a transom mount location, consider the following for
optimal performance:
• For your sonar to operate properly, the transducer must be
located in calm water. DO NOT mount the transducer behind
strakes, rivet lines, struts, fittings, water intake, discharge
ports, eroding paint, or anything that creates turbulence.
• Mount the transducer as close to the center of the boat as
possible.
• DO NOT cut the transducer lead. (This voids your warranty.)
• DO NOT mount the transducer in locations where it might be
jarred when launching, hauling, trailering, or storing.
• DO NOT mount the transducer in the path of the prop on
single-drive boats. The transducer can cause cavitation that
can degrade the boat's performance and damage the prop. On
twin-drive boats, mount the transducer between the drives, if
possible.
NOtE: DO NOT mount the transducer behind strakes, struts,
fittings, water intake or discharge ports, or anything that creates
air bubbles or causes the water to become turbulent. The
transducer must be in clean (non-turbulent) water for optimal
performance.
Fishfinder 400C Owner's Manual
tool list (not included)—drill, 3/8" wrench or socket, 5/32" and
1/8" drill bits, masking tape, #2 Phillips screwdriver, and marine
sealant.
To mount the transducer on a transom:
1. Position the transducer mount at the selected transom
location. Make sure the transducer is parallel with the water
line. Mark the center locations of each hole on the transducer
mount.
2. Using a 5/32" bit, drill the pilot holes approximately 1"
(25 mm) deep at the marked locations. To avoid drilling the
holes too deep, wrap a piece of tape around the bit at 1" from
the point of the bit.
3. Apply marine sealant to the 5 x 30 mm screws. Attach the
transducer assembly to the transom using the 5 x 30 mm
screws. Adjust the transducer assembly to extend beyond
the bottom of the transom approximately 1/8" (3 mm) on
fiberglass hulls or 3/8" (10 mm) on aluminum hulls. Adjust the
transducer assembly to be aligned parallel with the water.
4. Tighten the 10-32 locking nut until it touches the mounting
bracket, and then tighten 1/4 turn more. (Do not overtighten.)
5. Place the first cable clamp on the transducer cable
approximately one third of the distance between the
transducer and the top of the transom.
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