BE35 ENGINE ONLY PRODUCING 10' MP CAUSES PLT TO DECLARE AN EMERGENCY AND DIVERT TO A NEARBY AIRPORT. TRAFFIC ON RWY CREATES A CONFLICT SO PLT LANDS ACROSS THE RUNWAY AND HAS SUBSEQUENT RWY EXCURSION. NO INJURIES OR DAMAGE.

Narrative

5 MINS AFTER DEPARTING ZZZ THE ENG FALTERED AND WAS ONLY DEVELOPING ABOUT 10 INCHES MANIFOLD PRESSURE. I WENT THROUGH STANDARD RESTART PROCS; BUT COULD NOT GET FULL PWR. I TURNED THE ACFT TOWARDS ZZZ AND FOUND THAT I COULD MAKE IT; GIVEN THE ALT AND PWR AVAILABLE. AS I APCHED ZZZ FROM THE S I NOTICED THAT THERE WAS AN ACFT ROLLING ON THE RWY AFTER LNDG. I ANNOUNCED THAT IT WAS AN EMER AND TO CLR THE RWY. THE ACFT OPERATOR STOPPED ON THE RWY AND ASKED WHAT HE SHOULD DO; WHICH FORCED ME TO DISCONTINUE MY APCH AND FLY A PATH THAT WOULD PUT ME IN FRONT OF THE ACFT. I TOUCHED DOWN ON THE E/W RWY HDG NW. I CONTINUED ONTO THE GRASS AND STOPPED. THERE WERE NO INJURIES NOR DAMAGE TO THE ACFT. THE AIRPLANE WAS TOPPED AT ZZZ; HOWEVER; AFTER LNDG I DISCOVER THAT THE FUEL SELECTOR WAS NOT IN THE DETENT. I RESTARTED THE ENG AND TAXIED BACK TO THE FBO. THE ARPT MGR TOLD ME THAT CTR HAD CALLED BECAUSE THEY PICKED UP THE EMER CALLS. THEY WERE SATISFIED THAT THIS AS AN INCIDENT BASED ON THE EXPLANATION OF THE EVENT.