1 Syllable: S
dour, flour, hour, our, scour, sour
2 Syllables: SU
Bauer, bower, countered, coward, Cowper, flower, Fowler, Gower, hour's, housework, Howard, Howard's, louder, outburst, outer, outskirts, outward, powder, power, prouder, scoured, shower, soured, stouter, tower, trousers, voucher
3 Syllables: USU
devour, empower, encounter
4 Syllables: UUSU
overpower

Found 37 words across 4 groupings. Skipped 23 excess words of a similar stem.