A C180 FLOAT PLANE PVT PLT MAKES AN EMER OFF ARPT LNDG IN COOK INLET WITH A ROUGH RUNNING ENG AFTER A NORMAL DEP FROM LHD; AK.

Narrative

I DEPARTED FROM LAKE HOOD SEAPLANE BASE IN A C180 USING A STANDARD W DEP. I HAD PERFORMED A THOROUGH PREFLT; WHICH INCLUDED PUMPING THE FLOATS; CHKING ALL FLOAT ATTACHMENTS; ADDED 1 QUART OF OIL; AND FILLING THE TANKS WITH GAS. I TAXIED TOWARD THE W AND DID A RUN-UP AND EVERYTHING WAS NORMAL. I CONTACTED LAKE HOOD TWR AND WAS CLRED FOR DEP. THEIR SKY WAS CLR AND THE WIND WAS NEGLIGIBLE. TKOF WAS NORMAL IN ALL WAYS. UPON REACHING A SAFE AIRSPD AND ALT; I RETRACTED THE FLAPS AND BEGAN A CLBING R TURN TO THE N. AFTER TRAVELING ABOUT 1/2 MI; I BEGAN TO REDUCE PWR AND WHEN I DID SO THE ENG BEGAN TO RUN EXTREMELY ROUGH. A SMALL AMOUNT OF SMOKE CAME FROM THE R COWL; SO I REDUCED PWR. IT APPEARED TO ME THAT THE ENG WAS GOING TO FAIL AND THAT I NEEDED TO LAND IMMEDIATELY. I WAS AT 300 OR 400 FT AND WAS NOT CERTAIN THAT I COULD TURN AROUND AND LAND ON LAKE HOOD IF I LOST TOTAL PWR; SO I ADVISED LAKE HOOD TWR THAT I HAD AN ENG PROB AND WAS LNDG IN COOK INLET. I SAW NO OTHER ACFT NEARBY. THE INLET WAS ALMOST CALM AND THE WIND WAS NEGLIGIBLE. I SAW NO BOATS OR OBJECTS IN THE WATER OR ANY PEOPLE ON THE MUDFLATS NEARBY. THE LNDG WAS NORMAL WITH NO DAMAGE TO THE ACFT. I LANDED ABOUT 75 YARDS FROM THE SHORE AND WAS ABLE TO TAXI BUT THE ENG WAS STILL RUNNING VERY ROUGH. I CALLED LAKE HOOD TWR AND TOLD THEM I DID NOT REQUIRE EMER ASSISTANCE. AFTER SOME DISCUSSION WITH LAKE HOOD TWR AND ANCHORAGE GND CTL; IT WAS DECIDED THAT I SHOULD TAXI TO THE ANCHORAGE SMALL BOAT HARBOR WHICH I DID WITHOUT INCIDENT. I BEACHED THE ACFT IN THE MUDFLATS TO THE N OF THE PUBLIC BOAT LAUNCH; SHUT THE ENG DOWN AND WAITED FOR ASSISTANCE. I EXAMINED THE ENG AND SAW OIL LEAKING FROM THE #3 CYLINDER AND ASSUME THE ENG PROB WAS THE RESULT OF CYLINDER FAILURE. I DO NOT BELIEVE THERE IS ANYTHING THAT CAN BE DONE TO PREVENT SUCH OCCURRENCES.