Well, I finally bit the bullet and ordered a fish finder.  I bought a Lowrance Elite 4x DSI to use on the kayak.  Looking forward to finally getting a look at what is under the water.  So does anyone have any tips for mounting on a sit in kayak, or perhaps tips on how to use it?

I've never used this unit before. But Lowrance is the way to go. I would purchase a RAM mount to mount your unit to and then I would buy a rail system and a Screw ball to put on the kayak. Because they make a RAM transducer arm that connects to the screwball which connects you to the rail. Which eliminates you having to glue the transducer to the bottom of your hull. I believe this is easier and more affective.

Thanks for the input.  My kayak didn't have a rail system, but it did have a DIY dashboard located at the front of the cockpit.  It already had a Scotty mount for a rod holder installed on the dashboard.  I mounted the FF directly in front of this.  For the transducer I put together a mount using PVC pipe.  I used 1/2" PVC which fit perfectly in the mount.  I did have to notch one side to let it slide all the way in, but that helps it from rotating as well.  I managed to dodge the weather and got to hit the water this past Saturday, and it worked flawlessly.  Even when I ran into heavy surface weeds the tranducer hung on and never experienced any issues.  All total I believe the rig for the transducer cost me less than $10.  Of course most of that was in stainless steel machine screws and nuts.  Since I didn't have any primper/cement for the PVC bolting everything together actually came out a little cheaper.  If you have stuff to work with PVC you can probably get by for less than $6-7.  

 

The battery is where I spent a little extra money.  I bought a waterproof Plano storage box, and a Marinco trolling motor plug.  Using this I was able to create a water resistant battery box.  I found the idea online, and pretty much copied it exactly.  The box was less than $15, the plug/receptacle was about $20, misc part like connectors for the battery terminals, wire, heat shrink tubing added a few more $$$, but all total I spent about $45 on the battery box.  

 

Given all of this I have a fully functional FF mounted securely to the kayak and thanks to a great sale I managed all of this for about $155.  If anyone is interested in more detail or pictures just let me know.