Which factor is NOT considered when determining safe speed for a vessel?

When determining safe speed for a vessel, various factors are taken into account to ensure safe navigation and prevent collisions. Visibility conditions are crucial since they affect how far a navigator can see other vessels or hazards. Current weather patterns, such as wind and sea state, also play a significant role in how a vessel handles and the risks involved in navigating at certain speeds. The presence of navigational hazards is essential, as it directly impacts the ability to maneuver safely and prevent incidents.

Engine power capacity, while vital for operational considerations, does not factor into the determination of safe speed. Safe speed is more about the conditions surrounding the vessel and its ability to respond to those conditions rather than the vessel's engine capabilities. Therefore, the correct answer reflects that engine power capacity is not a determining factor in assessing safe speed.