This study compares four carbon intensity indicators applicable to harbor tugboats to identify the most representative greenhouse gas emissions management. Using operational data from SAAM Towage's fleet, the indicators evaluated traveled distance, operating time, energy consumption, and average engine load demand. Statistical analyses revealed that the energy consumption-based indicator exhibited lower variability and greater capacity to reflect the operational particularities of tugboats. In contrast, indicators based on average load presented high dispersion, limiting their applicability. These conclusions highlight the importance of considering vessel-specific characteristics when selecting indicators. This work provides tools to improve environmental monitoring and facilitates the implementation of sustainability strategies aligned with the maritime industry's emission reduction objectives.