"Thanks for all the replies.
"Thanks for all the replies.
Graham, The 15" pitch is magic on my boat in getting out of the hole fast, pushing the boat along fast (in choppy & windy conditions) at only third throttle (3400 rpm) and very responsive at throttle input and gets to about 5400 rpm flat out.
All this said, I used a few software programs that are used to calculate prop size and pitch and with all the data, gear ratio, rpm, weight of boat, hull shape etc fed into these programs, they all came up within a 1/4 inch of diameter and exact same pitch.
The calculated prop was a 13" x 19" pitch. This was fitted to the boat but what a let down - difficult to plane and had to run the motor well tilt up to get progress and if the prop was submerged, only run about 3000 rpm. I then pitched down to 17", better but not that effective and then down the 15" and my boat goes like a bat out of hell. This prop is a V tip.
I can add this: the altitude Im running my boat is about 1600 meters (5500ft) above sea level and hydroplane stabilizer fins are fitted to the Suzuki 85 hp. The total weigh with two persons aboard is about 900kg or about 2000 lbs."