I'm a maroon - A question about when to raise a draw.

[shadow29]

Raising flush draws (or any draw for that matter) has to do with equity edges. If your pot equity is 33% (which it is, approximately, for a flush draw) and there are 5 players (including you) in the hand you have a pot equity edge because your "fair share" of the pot is 20%. Combine this concept with a potential free card on the turn and possibly cleaning up pair outs, and there you go.