Green’s Dictionary of Slang

steamboats adj.

very drunk.

1985		M. Munro Patter 65: steamboats A picturesque if somewhat inexplicable word for drunk: ‘Look at the state of him – steamboats again!’.
1993		I. Welsh Trainspotting 116: Rents is pretty steamboats, cause ah’m feelin it n aw n ah kin drink that red-heided cunt under the fuckin table.
2000		J.J. Connolly Layer Cake 224: Have a double when the time comes. Don’t be getting steamboats and sloppy.
2001		G. Coughlan Everyday Eng. and Sl. 🌐 Steamed, Steamboats (v): very drunk – ‘we’re getting steamed (steamboats) tonight’.