Tugboats are essential for the operation of seaports. These have the functions of towing and helping those ships, barges or barges that cannot move by themselves; in addition, to escort ships containing dangerous goods. These vessels are mostly powered by a diesel engine of great power in relation to the size of the ship. The engine is the main element of a tugboat. The objective of this work is to estimate the risk weighting number for each of the engine failures, in order to prioritize maintenance activities and improve the reliability of the ship's engine based on this indicator. For this, the failure mode and effect analysis tool, the SAE JA 1011, SAE JA 1012 and ISO 14224 standards and the assessment of the severity, the occurrence and the possibility of detection each failure are used. The result is the division of the asset into 6 subsystems, 473 failures are identified in total, 17 of high risk, 28 of medium risk and 428 of low risk. It can be concluded that, most of the critical faults are in the engine cooling system.