I’m cursing like a race horse

This is a mash up of “cursing like a sailor” (swearing a lot) and “pissing like a race horse” (no definition required).   Not sure how the speaker could confuse cursing and pissing, although cursing does sound like coursing.  Of course, many of us have cursed AT race horses before, so that could be part of the mix-up.  Many thanks to Lisa O’Donnell, who heard this gem from a neighbor’s lips.