T.S. = Engine RPM / Gear Ratio * Prop Size / 1056

Example:

T.S. = (5500 RPM / 1.36) x (34"/1056) = 130.2 MPH

High performance boats average an efficiency loss between 10-20% due to hull drag and propeller loss.

130.2 MPH T.S. would translate = 104.16 - 117.2 MPH

What is the efficiency of your setup?