Nial Smith and Kevin Sinclair combined to take six wickets
Guyana then needed only 39 overs to reach 184-3.
Half-centuries led the successful chase from Tagenarine Chanderpaul and Shimron Hetmyer.
Chanderpaul led the way with 77 off 110 balls, his highest List A score, while Hetmyer finished not out on 62 off 53 balls, including five fours and two sixes.
Captain Tevin Imlach provided good support with 30. Shalome Parnell took 2-26 off six overs for the Scorpions, whose season ends with six losses and one no-result in seven matches.
The Harpy Eagles will join the Leeward Islands Hurricanes, the Trinidad & Tobago Red Force, and the Barbados Pride in the semi-finals.
The semi-finals are on November 8 and 9, while the final is on November 11. (Sportsmax)
Nial Smith and Kevin Sinclair combined to take six wickets
