Side imaging units use a combination of tightly-focused, super-high frequency beams to collect data in an extremely detailed manner, then take that data and "paint" an on-screen picture. "It's like taking an MRI of the water," explains Mark Gibson, senior brand manager at Humminbird. "The transducer reads a very thin slice of very dense, detailed info, then it moves on. The time-distance relationship allows the unit to determine exact distances and depths, and when you consider the overall area you can look at on your unit, you're able to cover literally 50 to 75 times the amount of territory that a traditional down-looker can see."
LENNRY RUDOWFlush-mounting is usually considered superior, and it protects your unit from the elements and from theft.INSTALLATION
Okay, so you know it's time to install a new fishfinder, and you're ready to roll up your sleeves and go to work. What's first? We'll assume you've already taken the old fishfinder off, and a new unit is ready to go. Wait a sec – when you removed the old fishfinder, did you also pull the transducer wire? We hope not. Leave the transducer wire in place, so you can use it to pull the new wire through the rigging tube easily.
Before you go to work, you'll need to make sure you have the following items on hand: a power drill and bits, a jig saw, a Phillips head screw driver, an adjustable crescent wrench, a wire fish, crimpers, a pocket lighter, a pencil, a new fishfinder head unit and transducer, 3M 4200 Fast Cure sealant/adhesive, 4 self-tapping #6 1-inch stainless-steel flat-head screws, 4 feet of 12-gauge tinned-copper shielded wire, with red insulation, 4 feet of 12-gauge tinned-copper shielded wire, with black insulation, two ring connectors, two butt connectors, adhesive-lined heat shrink tubing, nylon tie-wraps and masking tape. Be sure in all cases to use marine-grade materials.
Ready to flush-mount the head unit? Picking the exact location in the dash is imperative, because you need to ensure plenty of depth behind it (a minimum of 4 inches or so for most units) as well as enough space on the dash itself, which will depend on the size of the unit you have chosen. Remember, when it comes to fishfinders, bigger really is better, so take it as far as your dash and your budget allow.
LENNRY RUDOWIf you have to bring wires through the top of the helm when binnacle mounting, cover the hole with a clamshell fitting.The most common mistake people make at this point is failing to ensure that there are no accessories or wires behind the dash, in the spot they're about to cut out. Actually sawing before verifying the clearance can lead to significant damage of the electrical, steering, and/or control systems, so be careful when you measure.
Once you've chosen your spot, use masking tape to secure the cut-out template (virtually all of them have one included in the installation kit) to the dash. Using a pencil, trace the template directly onto the fiberglass. Then, using the power drill, drill a pilot hole for your saw blade in one corner of the template. Use a drill bit large enough to allow the saw blade to pass through the hole. Next, insert the jig saw blade into the hole and cut open the dash hole, following the dimensions of the template. Be sure to run both the saw and the drill at full speed; cutting slowly will only encourage the bit and or blade to grab and splinter the gel coat.
Once the cut-out is complete, you'll need to use a 1/16-inch drill bit to drill the unit's four mounting holes, which will also be shown on the template. Next, run a bead of 3M 4200 Fast Cure adhesive/sealant around the perimeter of the cut-out. (Note: some people prefer to use silicon as a sealant in this situation. Silicon will be easier to remove if need be in the future, however, it's far more likely to deteriorate over time and allow water past the seal. And while 4200 is tough to remove, it's not as difficult as 5200.) Add blobs on top of the mounting holes, as well. Then drop the unit into the cut-out, and use the included bolts to secure it. Tighten the nuts with your crescent wrench, and the unit should be securely in place.
LENNRY RUDOWMeasure twice, cut once. This installation caused problems, because the installer didn't measure the clearance between the throttles and the unit. Now, the port throttle can't be opened all the way.On boats with little flush-mounting dash space, it may be necessary to top-mount (binnacle-mount) your unit. This is far easier – simply drill four holes for the binnacle mount, run a bead of sealant, bolt the binnacle in place, and drill an additional hole to pass power and transducer wires through a clamshell fitting. But this mounting technique leaves the unit exposed to the elements and theft. Plus, it may partially block your view through the windshield. In virtually all circumstances, flush-mounting is the superior strategy.
Once the unit's in place, you'll need to measure the distance from its power leads to a terminal block. Cut one red and one black wire to size, and crimp one end of each to the power leads on the unit using butt connectors. Use your pocket lighter to seal the connections with adhesive-lined, heat-shrink tubing. Then crimp a ring connector to the other ends of each line. Do not, however, attach the power leads at this time.
TRANSDUCERS
Different boats may require you to mount your transducer through the hull, inside the hull or on the transom. Simply put, through-hulls will provide the best performance but require a pro – cutting a hole in the bottom of your boat simply isn't a DIY project. It is entirely necessary, however, on inboard boats, because turbulence created by propwash will ruin the unit's performance if the transducer is aft of the running gear.
