Krensen’s computerized engine controller can be set with parameters that match the stern drive’s torque ratings. Retaining the existing propeller is most likely an option, as the computerized engine controller and electric motor can be selected to match rpm and torque. However, changing the propeller may be desirable in order to achieve increased operational efficiency. In a retrofit, we will usually recommend that the stern drive be changed at the same time as the propulsion system. The main reason is that when an ICE goes in gear, it connects at 600 – 1000 rpm which can be really hard on the stern drive. This is avoided with an electric drive, as it can connect to the stern drive at 0 rpm. We recommend you start with a “clean sheet”, by replacing your sterndrive, so you do not have any unpleasant surprises.