I've fished with a Lowrance Mark 4 DI non GPS for about a year and a half. It did the trick and it came with the yak when I bought it. But it was small! So this winter, I saved my pennies, and picked up a new Lowrance Elite 7TI with the navionics card. I had to combine 2 - 7AH batteries in one box in order to get a full day of fishing. I use a Ram transducer mounting arm. If you don't need Side Imaging, the Hook 7 can be had at a reasonable price.