A marine vessel advisory system may be configured to calculate and provide operational information that show fuel consumption savings based on adjustment of vessel speed and/or heading. In an embodiment, the advisory system may operate real-time to collect operational and/or environmental conditions information to be used to calculate alternative operational performance of the marine vessel that will save fuel and reduce emissions. The calculations may include a simulation, machine learning, and/or artificial intelligence to determine a speed and/or heading of the marine vessel that will reduce fuel consumption. The advisory system may display the computed information for the operator, and the operator may elect to switch to the alternative operating parameters (e.g., slower speed). In an embodiment, the advisory system may interact directly with a marine vessel system and automatically cause the marine vessel system to adjust operating parameters based on computed operating parameters that saves fuel and reduces emissions.