I have an 18 foot flat bottom v drive with a 468 chevy. Tunnel ram set up with 2 660s on top. Took it out for the first time this weekend and power throughout the rpm range is great, however, at WOT (around 6000 rpms) I can hear the motor cutting out. If I back out of the throttle just a hair, the boat picks up more speed. Why is it lacking at WOT? I am also running a mag and tried to adjust timing to get rid of the problem but this didn't seem to help. Could I be running out of spark? Thanks in advance for your responses.