Research into the Propeller Strut for High Speed Outboard Motor

For better performance of outboard motors for high speed craft, improvement in the performance of the propeller strut located ahead of the propeller is indispensable in addition to ameliorating the performance of the screw propeller itself. Thus, it is extremely important to reduce the drag of the propeller strut, which accounts for the predominant portion of the submerged parts of the motor and hull when the craft is running at high speed and to improve the propeller efficiency in the wake of the propeller strut.

This paper, taking up two different shapes of the propeller strut, compares the performances of the propeller placed in the wake of the propeller strut in tank tests, and discusses the drag of the propeller strut. The two propeller strut shapes are that of a 70% scaled down model of the propeller strut SUZUKI's 200 PS outboard motor and its improved version. The propeller used in the experiment is one having super cavitating blades with the Pseudo-Kirchhoff nose, whose performance we have been analyzing systematically. Detailed comparison was further made of the drags of the differently shaped propeller struts by means of computational fluid dynamics.