Like Tex said get on plane and then back down. First you have to run it with as minimum gear and then with gear to see if weight distribution is the problem. May need to drop the engine one hole, Stainless Props give better performance. Play with your trim more, but defiantly get on plane first then drop down as slow as you want to stay on plane.
I always run a Hydrofoil for low and high speed performance.
http://www.cobramarine.com/cobra_mar...ro_series.html