ANSYS simulation results for a 300 HP two-stroke outboard marine engine gearcase running underwater at 75 mph shows cavitating surfaces, surface streaklines and surface pressure. This image also demonstrates the displacement and stresses on the gear meshing with deformation of internal components inside the gearcase.


During development of a 300 HP two-stroke outboard marine engine gearcase, BRP engineers found burn marks on the surface of the gearcase where the paint had eroded while moving at 75 mph underwater. Traditionally, they repaired such surfaces on test units with bondo work or grinding near the burn mark before testing again. However, in this case the burn patches appeared at different places and sometimes led to a loss of engine speed. Instead of resorting to temporary surface repairs, the engineers decided to try to better understand the cavitation and drag forces at work on the outside of the gearcase, as well as the effects of these forces on the internal components, to avoid the problem entirely. They chose ANSYS solutions to help them in this effort.


To optimize the design of the gearcase curvature, BRP used ANSYS CFX for hydrodynamic analysis of the gearcase. Quick and easy CAD modifications, meshing in ANSYS ICEM CFD, and simulations run in CFX eliminated the developmental testing and validating phase. These steps led to minimal cavitation while reducing drag on the gearcase surface.

Next, the engineers investigated the internal components of the gearcase using ANSYS Workbench and ANSYS Mechanical. The external forces acting on the gearcase surface were determined from CFX. For the first time, BRP engineers could see the pinion and gear meshing, gears distorting/bending, separation forces and contact/bending stress arising due to gear meshing, propeller shaft bending, clutch dog separating off the forward gear, gearcase surface stresses, etc. This simulation helped them to rapidly optimize and test the design.

Business Benefit:

This investigation lead BRP to offer a five year warranty — a new industry standard for marine engines. ANSYS simulations significantly reduced time and resources required for testing during the development phase.

Software used:

  • ANSYS DesignModeler
  • ANSYS Mechanical
  • ANSYS Structural
  • ANSYS Workbench