That prop you have is a 26 worked for holeshot and not top end. The best top end you will see with it is 80 when all the stars are aligned perfectly,and its sensitive to trim. Not the best driving or top end prop out there, but if your into river fishing its a must have. Your side-to-side issues are like Jazz mentioned. All over trimming issues and not chine walk. drop it back down to neutral trim and learn how to drive the boat before you go for big numbers with a different prop.