C150 ACFT IN CRUISE EXPERIENCED PWR LOSS. PVT PLT RECEIVED VECTORS FROM APCH CTLR AND DIVERTED TO AN ARPT FOR AN UNEVENTFUL LNDG.

Narrative

FLT ORIGINATED AT PAO ENRTE SBP. REACHED CRUISE ALT (OVER SJC CLASS C) OF 5500! SCATTED CUMULUS AT 3000-3500 FT PREVENTED LOWER CRUISE. CHKED IN WITH MRY (133.0) OVER HECKER PASS. OIL PRESSURE AND TEMP NORMAL. ENG HAD 5 QUARTS OIL ON TKOF. UPON REACHING A POINT ABOUT 6 NM NNW OF SNS; ENG LOST APPROX 300 RPM ABRUPTLY AND CONSIDERABLE VIBRATION SET IN. APPLICATION OF CARB HEAT AND MAGNETO CHKS DID NOT ALTER CONDITION. SUSPECTING AN ENG PROB; I NOTIFIED MRY APCH OF MY CONDITION. THOUGH PWR WAS STILL AVAILABLE; I DECLARED AN EMER AS APCH COULD GET MUCH WORSE WITHOUT WARNING. SCATTERED CLOUDS PREVENTED IMMEDIATE SIGHTING OF SNS ARPT. I REQUESTED A VECTOR FROM APCH WHICH DID CONFIRM MY NAV. FROM MY ALT THERE WAS LITTLE DOUBT I COULD REACH ARPT EVEN WITH LITTLE OR NO PWR. I REDUCED PWR TO LESS THAN 2000 RPM; WHICH REDUCED VIBRATION. MRY APCH TURNED ME OVER TO SNS TWR. ARPT BECAME VISIBLE BY 2500 FT AND I WAS ABLE TO LAND WITH NO TROUBLE ON THE ACTIVE RWY 26. I WAS ABLE TO TAXI TO THE TERMINAL. I NOTED OIL PRESSURE AND TEMP WERE STILL IN THE GREEN. A LATER RUN-UP ON THE GND SHOWED THAT 1 CYLINDER WAS NO LONGER PRODUCING PWR. AS OF THIS WRITING THE EXACT CAUSE IS UNKNOWN TO ME. THIS IS A RENTAL ACFT WHICH I HAVE FLOWN BEFORE.