Narrative:

On a VFR flight at FL175. ATC approved an IFR climb to FL210 for weather avoidance. While maneuvering to avoid moderate rain showers the left engine experienced a sudden loss of power. The engine continued to run; but produced no power. I decided to keep the engine running as the oil pressure was green and no visible signs of oil leaking. The engine would produce 0' thrust but did continue to run and provide enough power to operate the left alternator. I advised ATC and was given a lower altitude. I decided to divert to ZZZ. As my altitude got lower the engine began to respond with more power; but would not make more than 50% power. I was provided timely vectors to a GPS approach to ZZZ and landed. I had the engine inspected; and the attachment hardware for the inboard turbo charger waste-gate was found to be missing. This caused an imbalance in the induction system and loss of power. The hardware was replaced and an operational ground check to full power was made. Refilled and departed to ZZZ1.I probably should have taken advantage of [emergency] services that ATC provides; and would have done so if the engine had it quit or had to be shut down. Selection of the divert airport is often influenced by 'where can I get this fixed'. ZZZ2 was a bit closer; but has no facilities to inspect or repair this type of aircraft. I knew that there was flight training facility at ZZZ and assumed that there would be maintenance there. The aircraft also had a functional autopilot that without; I would have selected an airport further east and away from the rain and low ceilings that were in the area at the time.

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Original NASA ASRS Text

Title: PA-60 pilot reported diverting after experiencing a loss of engine power.

Narrative: On a VFR flight at FL175. ATC approved an IFR climb to FL210 for weather avoidance. While maneuvering to avoid moderate rain showers the left engine experienced a sudden loss of power. The engine continued to run; but produced no power. I decided to keep the engine running as the oil pressure was green and no visible signs of oil leaking. The engine would produce 0' thrust but did continue to run and provide enough power to operate the left alternator. I advised ATC and was given a lower altitude. I decided to divert to ZZZ. As my altitude got lower the engine began to respond with more power; but would not make more than 50% power. I was provided timely vectors to a GPS approach to ZZZ and landed. I had the engine inspected; and the attachment hardware for the inboard turbo charger waste-gate was found to be missing. This caused an imbalance in the induction system and loss of power. The hardware was replaced and an operational ground check to full power was made. Refilled and departed to ZZZ1.I probably should have taken advantage of [emergency] services that ATC provides; and would have done so if the engine had it quit or had to be shut down. Selection of the divert airport is often influenced by 'where can I get this fixed'. ZZZ2 was a bit closer; but has no facilities to inspect or repair this type of aircraft. I knew that there was flight training facility at ZZZ and assumed that there would be maintenance there. The aircraft also had a functional autopilot that without; I would have selected an airport further east and away from the rain and low ceilings that were in the area at the time.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.