Green’s Dictionary of Slang

(Aus.) the throat.

1982		G. Newbold Big Huey 251: Motorboat (n) Throat.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 13: Taking a gargle and clearing his motor boat the Beecham commenced.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 119/1: motorboat n. throat.