What was found
HVN-PHL FLIGHT#3702. CREW REPORTED AFTER CLIMBOUT AT 16,000 FEET, #1 ENGINE OIL PRESSURE BETWEEN 40-45 PSI. NUMBER ONE ENGINE SHUT DOWN, DIVERTED TO LGA, EMERGENCY DECLARED. MAINTENANCE FOUND ENGINE FORWARD BREATHER CARBON SEAL NICKED,CAUSED BY DISTORTED MATING SURFACE OF MAIN ACCESSORY GEAR SHAFT ASSEMBLY. CARBON SEAL REPLACED. ENGINE ASSEMBLY REPLACED IN ACCORDANCE WITH JOBCARD 008-71-01-349, PRATT AND WHITNEY MAINTENANCE MANUAL 71-00, AND DEHAVILLAND DASH 8 MAINTENANCE MANUAL 71-00. LEAK CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.