as mentioned, i've small flat screens mounted on anchor locker lid or on a swivel/arm mount on backside of the bathroom/head wall.
but, IMO, i'd skip the whole TV idea unless it is particularly to play DVD's or you're planning to get a sat dome, TV, phone, and data package.
Rather consider a tablet device and watch downloaded TV shows or TV via wifi or internet.
i don't watch TV on my iPad, but when out of wifi range, i do utilize bluetooth and my iPhone's data connection to make a hotspot for internet connection for iPad. There's much more you can do with a tablet and internet than a TV.
Pro's of tablet: portability, cost, no installation, no wires, internet, no drain on house batteries, no worries of corrosion from marine environment, and usually you can find free or cheap wifi or use an existing data plan to get internet thus saving some $ in long run.
Cons of tablet: must download movies to view, smaller screen size than average 15-20" TV's installed in small cabins,
FYI, DVD's and in particular DVD rental stores are going the way of the Dodo bird. Writing is on the wall for movie rental stores. All major stores in my town have closed and only a couple small independents operating. Even Netflix's bubbles is deflating as other options are emerging.
A tablet with marine GPS app can also double as emergency back up plotter!
