The marine diesel engine is a marvel of machinery, producing unique sounds that are crucial to understanding its condition. Unusual noises may crop up whether you're underway, docked in port, idling or at anchor. These noises might signal potential problems with your engine or propulsion system. Here are five unusual sounds from your marine diesel engine and what they could indicate: 1. Pinging Or Knocking Noise A "pinging" or "knocking" noise is a common cause for concern.