Propeller for marine propulsion drive

摘要

A blade design for a counter-rotating propeller system improves the performance of the outboard drive on which is it employed when the propellers are run partially exposed. The propeller system includes a pair of counter-rotating propellers that rotate in opposite directions about a common axis. The rear propeller has a smaller diameter-about 92% of the front propeller-and a total blade face surface area of about 85% of the total blade face surface area of the front propeller. The blades of the front and rear propellers desirably have the same camber and generally the same pitch. The rear propeller pitch is between 90% and 110% of the front propeller pitch. These blade parameters improve the efficiency of the rear propeller over prior designs when the propellers run partially exposed in order to maximize the thrust produced by the propulsion system.