I have a 30' Avanti and just swapped 300x's for merc 250 efi's LH (port)and RH (starboard) rotation. I had 14 5/8 x 23 stainless worked props with the 300x's and the boat turned low 70's. Just borrowed a pair of 14 5/8 x 21's and the 250's are nailing the rev limiter within seconds after literally JUMPING on plane. I have hit a max speed of 59.7 with the 21's. I just put a spare pair of 14 5/8 x 23's on the boat (didnt think the 250's would push them). The boat slowly gets out of the hole and hits a max speed of 61 and the boat is still hitting the rev limiter. I loved the performance of the 21's, but the speed wasnt there. 21's also held plane down to about 15 mph and and I could get on plane with 1 motor. What can I do to keep the performance of the 21's, but increase speed and stop hitting the rev limiter at full throttle?? Any help would be greatly appreciated. Adrian ajacobs@sprint.blackberry.net