1 Syllable: S
auf, aus, blouse, boughs, bouse, bout, bows, brows, browse, clout, couch, cows, crouch, doubt, drought, gout, grouse, house, How's, louse, mouse, mouth, oust, out, ploughs, plows, pouch, rouse, rout, route, scout, shout, snout, South, spouse, spout, sprout, stout, Strauss, tout, trout, vouch, vows
2 Syllables: US
about, allows, arouse, devout, endows, espouse, redoubt, throughout, without
3 Syllables: UUS
thereabouts

Found 53 words across 3 groupings. Skipped 19 excess words of a similar stem.