catbass
Thanks for the links, I have a sit in, and the whole back compartment opens so I figure I could put the transducer back there right behind the seat but I haven't the slightest clue on how to attach the unit itself to the kayak
catbass,
I have a Hummingbird (Piranha 2, I think) fishfinder for my kayak. It works well enough, gets you the depth and picks up fish. The mount that it came with for the display portion works well. Just plan it a little with your rod holders and paddle, so that it isn't in the way. I mounded mine a bit forward, and have to lean forward to reach it, but usually just power on and off.
Mine is also sit in, and tried the through hull mount. Being sit in, the hull has a bit of flex when you sit it on the ground ect. This flex will eventually pop, just about any glue/epoxy mounting your transducer. The polyethelene doesn't really bond well to any glue that I know of either. Possibly a better bond if you ruff up the surface a bit? I had used 60 minute epoxy and was a pain in the butt to clean off of the transducer after. I used silicon, which worked for about two trips. After that, I just used a wad of petroleum jelly and duct taped the transducer down. This actually held longer than the silicon, and much easier cleanup... If using a good bit, external mounting is the way to go. Just be very careful that you don't put your fastener holes below the water line.
As for power, I had an old 12V drill battery (Black & Decker Firestorm) that worked perfectly for a power source. It would last a 10 hour fishing day, and a little larger than a hockey puck size needed.