Riche, not sure what you mean by "main gate". For Scorpian Bay you take the western entrance to the park which is west of the dam, take a right like you are going to the 10 lane ramp, and then go straight to Scorpian Bay rather than turning right toward the 10 lane. Later you will turn right into Scorpian Bay. The route is well marked at every turn.
Hope that helps.
Hope that helps.