Duo -Prop designs used by leading outboard manufacturers are facing technical failures in 325HP to 350HP range. Considerable effort is being exercised to keep a close lid on this issue until a solution can be found.
The propeller shaft is cantilevered and supported by bearings at the rear end of the torpedo. The front end is only held in place with a bush which prematurely wears out due to the impact torque created by gear engaging of the heavy duo-props. The high moment of torque exerted by the excessive distance between the aft propeller and the bearing support as shown in the picture below causes high lateral stresses on the bearings. This in turn acts on the small aluminum lip on which the total axial forces of the propeller shaft acts forces the lip to wear out allowing excessive play and seal failure leading to a combination of water ingestion and failure of the pinions.
