First time I've run this boat with four adults (about 850 lbs worth, Usually run two adults and two kids). When water started getting choppy the prop started slipping before I could get on step. Motor appears to be mounted correctly. Prop is a 15.5" dia x 15" pitch Rubex 3. I'm thinking I may want to switch to a four blade prop. When running with me alone and about 10 gallons of fuel (1/2 tank) rpms max out at about 5100 and gives me a speed of about 34 mph (gps) on moderately calm water. I was thinking of going to a Rubex 4, 15 x 13 but I'm wondering if dropping 2" of pitch is too much of a drop? Any thoughts?