Hey Jax,

Each AA battery is 1.5 volts so 8 in series will give you 12 volts. Most units actually have a working range of from 10 - 16 volts or so, so you can also use a 10 pack which will give you more battery run time. Also, since you have the straight X4, you will have less power consumption than with the pro so good move there. I got the Garmin Echo 100 last spring and its about as close to the X4  as any unit out there. I don;t use it as heavily as you intend to, basically just checking for occasional depths, reefs and drop offs then turning it off. On my spring trip, using regular Alkalines, it lasted the whole 5 days easy. The last 2 days I kept it on all the time I was fishing to test when the batteries would wear out. They didn't ( 4-5 hours a day). I then used those same batteries on a few more trips that summer, although not keeping it on all the time. Even if you take 2 sets of back up batteries, the AA's are so light its way better than standard portable set ups. I have some pics of mine so I'll post some (they are also posted on BWCA.com). As to your hull, I have heard aluminum may not work but I heard teh same thing about cedar strip hulls and it works fine shooting through my cedar strip hull. I used a foam cut out siliconed to the hull, add a few drops of water and then place the ducer in there. That way my transducer can be removed for car topping and winter storage etc. I put the battery pack in a starfritt water tiight plastic container from Walmart.

Moonman.