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IMPORTANT Read and understand manufacturer's instructions for installing their unit BEFORE proceeding with this installation. This installation will show you how to mount a transducer, put cables through the deck (and make it water tight), to tuck the cables inside the hull and install the battery box.
Mounting the transducer: Turn the kayak over and find the flattest area of the hull. This is where you will want to mount the transducer on the inside of the hull close or next to the scupper holes (which is the strongest area of a hull and has the least amount of flex) that you can easily reach. Using emery cloth (150) lightly sand to rough up the area where you are going to mount the transducer. Wipe area clean with a rag. Most manufacturer's recommend using a two-part, slow cure epoxy. This works well on a hard surface, but most kayaks area made of plastic and are flexible. "Marine GOOP" is a silicone based adhesive and will give and stretch with the bumps of the road, waves, and other movements.
Using "Marine GOOP" cover the bottom of the transducer with no air bubbles in the GOOP. (About the size of a quarter for the transducer shown. Your brand may require more GOOP) . Place the transducer on the area pressing down and moving it from side to side just a little bit until it is all the way down against the hull. Now place a weight on top of the transducer and let it dry for 24 hours. The kayak must be sitting level or the transducer will start moving.
Check to make sure that the transducer doesn't move during drying
Mounting Display Unit: Before mounting your fishfinder, mount your rod holder(s) first and then select an area suitable for your display unit. Locate a suitable area for the display unit (photo A). Drill hole just big enough to fit plugs through. (Photo B below shows drill bit and plugs and photo C shows the mount with the hole drilled into kayak).
BE VERY CAREFUL WITH THE KNIFE in this next step. Using a rubber stopper, you will make a grommet. Cut stopper in half (See photo D). Cut two grooves about 1/8" deep all the way around and 1/8" apart (Photo E). Now make a trough in the stopper (Photos F shows it started and photo G shows it complete. Click on images to see them larger). Now Drill 2 or 3 holes in the stopper depending on the unit you have. Use a drill bit just slightly bigger than the cable (See photo H). Slice the stopper from the outside to the holes from 2 or 3 different sides (see photo I). Now you have a custom grommet. Pull cables through the hole in the deck and put them into the grommet (see photo J). Using a screwdriver, work the grommet into hole (see photo K). It should look like Photo L now. Also see picture M for the inside view. Now mount the base. Note: I like to use nuts and bolts for all mounts when I can reach the inside area see photo N)
Mounting the Battery Box: Cut a pool noodle in half (the width of the box) and using GOOP glue this to the back of the box (See photo O). Let dry for 24 hours with weight on top of the box (the battery works well for this). Place the box inside the front of the kayak. Using a felt tip maker, run the marker along the hull while marking the pool noodle (see photo P). Trim the pool noodle down the line, stay to the outside of the line. (see photo Q).
Place the battery into the box and using GOOP secure the pool noodle to the box (see photo R). Let this dry for 24 hours. Drill a hole in the box for the cable and secure it with a plastic cable clamp (see photo S). Using an emery cloth, rough up the area and wipe clean. With the battery in the box for weight, use GOOP to glue the box down in the hull. Let this dry for 24 hours. During the first hour check every now and then to make the battery box is not sliding. Now put a water tight fuse and two female flat connectors to the wires (see photo T).
The last thing to do is to tuck the cables up and secure them using zip ties, rubbing alcohol and zip tie anchoring attachments. Sometimes the peel-and-stick zip tie attachments do not work well on certain kayaks, so you would want to use the plastic cable clamps attaching them to a mounting bolt on the inside of the kayak