I cover my fishfinder with a cloth bag, or you could cover with piece of cloth and tie a string around the base. It keeps sunlight away from the screen.
I use a Fish Easy 350c and a 320c, I got the 350c with no transducer for under $20 off of ebay and it suits me fine cause mostly I am cheap Screen is color and does show fish.
I had bronze transducers already in the hull. I coupled one to a garmin 6 pin transducer, wired it myself since no wire converter exists, the other to an airmar 7 pin transducer. You can get a socket to match the transducer plug. Had to add var resistor for temperature compensation. So speed, temp, depth all working for them both.
modded Eagle using plugs from an old Apelco 7 pin transducer and the power plug also. This one is up on the fly bridge in the weather, but covered.
The 350c, I just ran a power wire thru a drilled hole, that one I hooked up to a 6 pin garmin transducer and it stay dry in the cabin.
Some pics I took of the wiring.
https://picasaweb.google.com/105248911187594415233/EagleAirmarJune122015?authuser=0&feat=directlink
Reusing the existing transducers with these cheap head units, I saved some money and learned they can coexist different brands with some mods.