Sunil Ambris' first ODI ton ensured Andrew Balbirnie's fourth came in a losing cause as West Indies completed a tri-series double over Ireland at Malahide to secure a spot in the final.
Ambris' 148 guided West Indies past Ireland's 327-5, in which Balbirnie scored 135 from 124 deliveries, with 13 balls to spare as Jason Holder's men won by five wickets to move top of the table with a second victory in three.
West Indies beat Ireland in their first meeting of the tournament at Clontarf last Sunday when Shai Hope and John Campbell posted the highest opening stand in ODI history of 365.
West Indies will play either Bangladesh - the side they lost to by eight wickets on Tuesday - or Ireland in the final on June 17, with Ireland needing Holder's men to beat Bangladesh on Monday to keep their hopes alive.
Balbirnie, who struck 11 fours and four sixes, shared a 146-run stand with Paul Stirling (77) for Ireland on Saturday, while Kevin O'Brien hit 63 from 40 balls and Mark Adair added an unbeaten 25 from 13 deliveries.
Ambris then top-scored for West Indies, though Holder (36), Roston Chase (46) and Jonathan Carter (43no) also played their part for the tourists.