Boeing a/t

HiHope you don't mind a question about the B737, I realise you have all moved up to bigger iron ;-)Actually this question may also apply to the 744 which is another question.If I understand this correct on takeoff the SPD window should be bugged to V2 and selecting the A/P (after t/o) adds 15 KIAS to this value. Does the SPD then change to the FMC speed at the acceleration ALT or when/how ? also the V2+15 is still below clean speed isnt it ?Also, what if I want to hand fly for a time, I get a flashing A (I think its an A)is this as the SPD is too low ?Perhaps somebody could explain the correct procedure and logic behind the a/t use in a takeoff for both A/P on 'soon'after t/o and hand flying.MTIASteve (UK)