there are systems that have their own tank, and systems with an inlet strainer
the systems with an inlet strainer appear to get plugged after a while. for example, the taylor made system comfort zone
http://www.taylormadeproducts.com/czone/ you also dont want to install such a system if you are on salt water unless you like a fine coating of salt all thru-out your interior
I would suggest a system with its own tank, especially if you boat in water high in minerals, debris, tanic, etc or in salt water.