What was found
(CAN) IN CLIMB, ABOUT 60-70 FEET ABOVE WATER (OTTER ON FLOATS) A LOUD BANG WAS HEARD, ENGINE LOST POWER. PILOT DESCENDED RAPIDLY, AND LANDED SAFELY. GROUND RUN LATER, ENGINE WOULD NOT GO OVER 1400 RPM, AND VERY ROUGH BETWEEN 1200 AND 1400. LATER INVESTIGATION SHOWED NR 4 CYLINDER EXHAUST ROCKER ARM BROKEN, NOT ALLOWING EXHAUST VALVE TO OPEN. ALL EXHAUST FROM NR 4 WAS GOING INTO INTAKE VALVE, CAUSING ENGINE TO QUIT OVER 1400 RPM.