Engine Malfunction Leads to Ditching off California Coast (N141CM)

Incident Overview

The pilot reported that approximately 150 miles southwest of Monterey, the right engine began producing unusual noises, running rough, and showing high cylinder head temperature at the limits of the gauge. The pilot advised Oakland Center of his position and situation but did not declare an emergency. Attempts to open the right engine cowl flap were unsuccessful due to a malfunction. The pilot then increased fuel flow to the right engine to cool it, eventually reducing power on that side to maintain operation. To compensate for the asymmetric power, the pilot added power to the left engine, increasing fuel consumption beyond planned burn rate. The flight attitude required by asymmetric power led to periodic unporting of the outboard fuel tank pickups. The pilot switched to inboard tanks until exhausted, then attempted to feed from outboard tanks. Unable to maintain consistent engine power, he was forced to ditch 20 miles short of the coastline. The VFR flight plan indicated 13 hours 10 minutes en route with 14 hours of fuel; the lapsed time from departure to ditching was approximately 13 hours 12 minutes.

Probable Cause

The official probable cause is: An undetermined system malfunction in the right engine, which led to an increase in fuel usage beyond the pilot's planned fuel consumption rate and eventual fuel supply exhaustion.