OVERHAUL SERVICE MANUAL:

INTRODUCTION TO JET DRIVES
Berkeley Jet Drive Specifics

The Berkeley jet drive is a mixed flow design (part axial flow, part centrifugal) with a 12" size designation.  This 12" size designation is from water well sizing, meaning the bowl will fit in a 12" well casing.  The original technology for Berkeley comes from the hydraulic principals used in the design of single through multi-stage line shaft turbine pumps which are used for submerged application in all types of water well or fluid transfer systems.

The balance of centrifugal and axial flow pump characteristics assures you of adequate thrust velocity for good performance in the popular boat speed ranges from 30 to over 60 MPH.  The efficiency of the jet drive is readily seen once speed in the 40 plus miles per hour ranges are reached.  Minor changes in the nominal 3¼" diameter nozzle are possible and may be effective in fine tuning.  Usually a slightly larger diameter for boats with top speeds below 45 MPH and a small decrease in nozzle diameter where speeds above 65 MPH are possible.