I installed it on mine. It's and easy install but you will need the electric accessory unit for it to work. The depth finder works when going slower than 15 good. In choppy water or fast it will not read.
I had mine installed by my dealer. It tracks at all speed except in chop as mentioned. When I trim the nose up it gets less accurate as you might expect. I really like having it. It has let me a better understanding of the depth of the different regions of the lake where I ride.
I guess I always wanted one, but $400 is crazy!!! The profit margin must be HUGE. Other depth finders are $100 (which I'm thinking about looking into). I know that those won't integrate into the Spark's display, but still ... $400?
I'd like one, but for me, I've studied the local charts and where I ski, if its shallow, I can easily look down through the turquoise water and see the white sand.