From the Ercoupe Type Certificate Data Sheet - A-718

Control surface movements Serial Nos. 113 and up: (S/N 112 and below not available)
Elevator Up 13° Down 12°
Aileron Up 40.5° Down 9.5°
Rudders Outboard 20° Inboard 3°

So there you have it. Rudders deflect 20 degrees outboard and 3 degrees inboard.