I have a small Rule that goes to a thru-hull, it always gets clogged. I bought all the stuff to install a macerator including a larger hose and larger thru-hull. I have yet to install it, because of other mechanical work. But I think that is the only good option. My box used to have a drain in the bottom, but I keep my boat in a slip and didn't like having a rubber plug in a drain the whole time, so I plugged it. Good solution if a trailer boat though.
Glenn (Wizard)
"The Reel One"
26' Billfisher