While flying off the coast of Waterford at Bunmahon, the pilot experienced rough running of the aircraft’s engine. At approximately 600 feet above mean sea level (AMSL) the pilot levelled the aircraft from a climb, turned on the fuel pump, switched the fuel tanks and quickly turned on the carb heat. There was no improvement in engine performance. The pilot observed a field large enough to make a landing. He landed with little damage to the aircraft and no injuries. He used his radio to report the incident to the control tower at Waterford Airport. The aircraft also suffered an engine failure on a successive flight. Possible causes in both cases were rich carburettor settings and poor magneto spark with perhaps a case of induction icing during the incident flight.