Medium speed diesel engines are the most common power in the marine industry. These machines are used as the vessels main engines, auxiliary engines and as emergency energy supplier. Last decade more and more high speed engines are used as auxiliary engines. The main problem is that number of the engines damages appear without any symptom. Crankshaft failure is the most expensive damage to medium speed engines but beside the crankshaft the engine has number of not so expensive items but extremely important for normal operation as cylinder liner, piston, connecting rod, etc. Statistics shows that cracks in these parts could lead to engine total loss with further consequences. The sources of these cracks are the engine overloading, non- compliance with manufacturing technology, material fatigue, etc. In order to prevent drastic consequences, detection of these cracks in the very early formation stage is extremely important [5], [6], [7]. There are different methods for the engines control, as vibration, tomographic, acoustic emission (AE), etc. We focused on AE method implementation for the engine condition control.