I have a 2003 Tohatsu 90 TLDI on a 20' skiff. When the boat and motor were new 3 years ago, I went with a 13.75x15 Michigan Vortex alum prop which would get 5700 rpm when lightly loaded. Operating range is 5150-5850 rpm. Now after three years I've added a windshield to my center console, an...