Or search: float, impel, launch, plunge, propel, commence, displace, smoothen, launching, actuation, propulsion
2 Syllables: SU
bondage, bronzes, calmness, commas, Congress, conscious, dauntless, dramas, fondest, fondness, genres, haunches, homage, honest, jaundice, Johnson's, longest, longings, Longmans, Monmouth, monstrous, omnis, pompous, pontiff, promise, promptings, promptness, Psalmist, Romish, strongest, Thomas, Thompson's, Thomson's
3 Syllables: SUU
pianist
3 Syllables: USU
accomplice, accomplish, admonish, Adonis, astonish, belongings, dishonest, responses, responsive, subconscious, unconscious
4 Syllables: UUSU
unresponsive

Found 46 words across 4 groupings. Skipped 5 excess words of a similar stem.