I can help.
First, get out your straight edge and square.
Set all of your trim tabs so that they are 100% parallel to the bottom. Not even, but parallel. This is the number one issue with the boat not turning. It needs zero right outer tab to turn. It does fine on it's own.
Set your turn fin(s) so that they are exactly 90 degrees to the bottom. Not 89 or 91.
Make sure you have a strong rudder servo (150+ in/oz). Digital preferred.
Make sure your prop is thin and sharp, not just sharpened at the edge. If you want to try another prop, try a 2716/2-20 by one of the excellent prop guys like G-force, DasBoata, Bob Austin, Mark Sholand, Brent Daily, etc.
If you want the boat to go straight with a strong engine and little to no left rudder, move the stinger to the right 1/4 inch. this helps a bunch, but is not needed with a stock or mild motor.
Call me if you want to talk about it.
(866) 922-9477