ran my boat this weekend. 16'flat bottom skiff,1998 15hp 4stroke suzuki, cav. plate level with bottom of hull, two full size people in the boat with all our fishing gear,i have a 9 1/4 x 9 alum prop, the motor ran @ 5600 to 5700 rpm's and GPS said 21 mph. the book says 5500 to 6000, and the rev...