Help boat problems
You haven't stated what ESC you have so it's a bit difficult to give advice.
Most ESCs require some initial set up and it sounds like yours needs adjustment.
If you can work one servo OK you presumably have a separate Rx battery?
Many ESC's have a built in BEC and don't need a separate battery.
There are 5 channels on the Planet so its important that you are using the correct channel for your rudder and ESC. You can use the rudder servo to select the channel you want to use for the ESC then plug the ESC into that channel and the servo into the rudder channel.
We need to know what ESC you have to give further advice?
Dave
Dave