If you just have to get the best motor, take the one from offshore electrics,,, But, there isn't much difference between that and the 8.4 bb motor, you'll hafta decide if it's worth the extra money. I would start with a basic 42mm prop, such as an X442, later for speed maybe an X445, or X645 but make sure to check your motor heat along the way. I assume your using a cooling coil.