Scupperlip

Scupper: (noun) The plumbing drain cover of a floor drain or the deck drain of a boat/ship thats used to drain everything from mop water, through fishing guts down to raw sewage drainage out in the open sea.

To call someone a "scupperlip" is a naval term to say that someone talks a lot of shit

"Seaman Nelson sure talks a lot of scupperlip"