depth/fishfinder 13.5 Boston Whaler

I have the old--blue--13.5 Whaler with a new 40Hp Yamaha. Use in on
the coast in South Carolina--in the streams and marshes near the
ocean.Would like to add a depth/fishfinder that can be mounted on the
console and not have to drill any holes, etc in the boat.Maybe a
GPS/depth/fishfinder. I would like one that is easy to read--As I get
older my eyesight is no longer as good.....This is my first search for
help----Would love to hear anybody's recommendations. Please email me
at --------Fred---retired USMC---Thanks for
any help.