Set up the wiring for the Fish Finder. With the transducer in place, using the 5/32-inch drill bit drill a hole completely through the hull on the transom above the transducer and waterline. Push the wire through the hole and up to where you will be mounting your console. Make sure to tack this wire out of major walkways so that it isn't cause for tripping.
Measure the distance between the main battery bank, the console and the transducer. Cut 12 gauge wire into lengths long enough to reach from the boat's battery bank to the transducer and console, and then connect the appropriate wires to the negative and positive terminals. Once you've connected the wire to the battery, twist it to create an anti-EMF (electromagnetic field) so that it doesn't interfere with the other instruments. Tack the wires in place with staples or electrical tape.