I can attest to the fact that throwing 90+mph from the OF as a HS'er will get you attention from RC's. Son threw 91 and 92 at a showcase when he was 16, and it got him a lot of attention. It seems that earlier in the thread that having a strong arm is somehow equated to being an incompetent fielder, rather than looking at it for what it is, a positive attribute. For every OF arm that is in the 90's, there are 25 that run a sub 7 60.
I don't know the answer to the OP's question, but will venture a guess that high 80's would be good enough for the RF/CF at the D1 level, assuming that they can hit, and run reasonably well. There is no absolute answer, as any player can be more, or less, than the sum of his "tools", but I will say that 90+ does get you noticed.