Several years ago at a Lake Powell C-Dory Gathering, I rode as an observer, so C-Brat Tex could water ski behind their CD22 with his wife Sharon driving. I believe the motor was a Mercury 80 hp 2 stroke & even at the elevation of Lake Powell it went well, so I think a tube with the 115 hp should be ok. Of course this could depend upon additional weight in the boat & size & number of people in the tube.
Jay