Eagle Cuda 350
I have this fishfinder/GPS on my Oday 22. I mounted the transducer below the V-berth with epoxy on the fiberglass sole (floor), making sure it was ahead of the keel. I could have mounted it on the sole below the cockpit or on the transom at the water line but I want to know about shallows before the keel encounters them. The only down side I've seen about mounting it inside is it doesn't give water temp, it gives the interior temp. The head unit is mounted in the cockpit on the cabin. I remove it when I'm not using it to protect it from the weather.
It's not easy reading the screen from 5 feet away while you're trying to navigate. I taught my 9-year-old to read the speed and depth so, no worries!
I couldn't find any other fishfinder that gave me speed and depth for that price. If that's the limit of your budget, I'd recommend it. If you have $1000 or more to spend, look for something with a bigger screen.