Code of Federal Regulations Title 46. Shipping § 46.58.25–50 Rudder stops

(a) Power-operated steering gear must have arrangements for cutting off power to the gear before the rudder reaches the stops. These arrangements must be synchronized with the rudder stock or with the gear itself rather than be within the control system for the steering gear, and must work by limit switches that interrupt output of the control system or by other means acceptable to the Commanding Officer, Marine Safety Center.

(b) Strong and effective structural rudder stops must be fitted;  except that, where adequate positive stops are provided within the steering gear, such structural stops need not be fitted.