I'm going to assume here that you are talking about a manual bilge pump. My friend has a 1978 C&C 30 mkI. His manual bilge pump is located on the cockpit sole slightly to port and forward of the steering pedestal. This was where C&C installed it from the factory and was not an owner installation. You should locate a manual bilge pump accessible from the helm. In any event, it shouldn't be difficult to trace a 1.5" diameter hose from a through hull fitting back to it's origin. The bilge pump may have been an option back in 1973.