Mount the TransducerThere are a few places you can mount the transducer, inside the hull, over the side, or thru the scupper. Now there may be some other locations but these are the three most popular locations. Deciding where to mount your transducer depends on a few different factors. What kind of fishing do you like to do, deep lakes, shallow or small water, blue water, river, etc. Basically will your transducer be exposed to damage. Next you want to consider the type of fish finder you have. Most standard fish finders will work well in any location you choose. DSI or down scan imaging fish finders, like the one I'm installing today, may not work well when inside the hull. While some people may have luck with this type of installation, Lowrance specifically states in their mounting instructions that thru hull installations are not recommended because it significantly degrades the DSI performance.
Because my fish finder is a DSI I'm going to mount thru a scupper hole for direct access to the water and hopefully best results. One note before I continue, there are plenty of discussions about turbulent water around the scuppers causing less than desired performance out of your transducer. I made the decision to ignore these discussions after I came across a scupper transducer mount made by Lowrance.
With all the above said, here's how I did mine. I started with a threaded plastic tube from the plumbing department of Lowes. Cost about $1.50. I added a cap to help retain the pipe from falling through. I used a 1" diameter pipe but the size might be different depending on what will fit through your scupper. Measure your scupper and head to Lowes or Home Depot.
Next you want to screw the cap on the pipe, thread it down only about half the threads. This will give you a little room to tighten things up. Insert the pipe with cap into the scupper with the cap on the top side of your kayak. The next part is the only tricky part of the installation. With the pipe sticking thru the bottom of your kayak, you'll need to eyeball how high you can mount the transducer mount onto the pipe and mark it. Take the pipe out, and cut it off about an inch below where you marked. With the pipe cut to length, drill the mounting hole for the transducer. Last you'll need to cut one side of the pipe about 1/4 to 3/8's wide up to the mounting hole. What you'll end up with is something that looks like the picture here. Notice I also drilled the top of my cap for the wires. This may not work for your setup but is an option.
Mount the DisplayOkay the hard part is done. Now to mount the display to your kayak. Choose a location that won't interfere with rod placement, casting, etc. It was also very important to me to be able to reach my fish finder from my seat without needing to get out of my seat. I chose the the center hatch cover of my Jackson Cuda. This process is pretty simple, decide where to mount it, drill the holes, and be sure to use stainless steel hardware.
BatteryThe battery is a place you'll need to do a little math before purchasing to ensure you get the right one. First, check what the voltage requirements are for your fish finder. Next is to determine the Ah or Amp Hours you'll need. To determine this you multiply the amount of run hours you want times the mA draw of your fish finder and divide that sum by 1000. This number will give you the Ah you'll need. For example, if you want your fish finder to run for 12 hours and it has a 210 mA draw: 12(210)/1000=2.52Ah
This means a 12volt 5.5Ah Werker battery will run your fish finder for over 24 hours.
There are many ways to mount your battery. I chose to purchase a small tupperware style container with a locking lid. I velcro'ed it to the bottom of my hull and then velcro'ed the battery within it.
Edit 7-6-2013: Here's one I can totally credit to the fish finder. I saw her on the finder and continued to paddle past. I turned around the kayak and casted a crank bait and the fight was on! (sorry for the white legs!)