How can excessive weight affect a vessel in terms of stability?

Excessive weight on a vessel significantly impacts its stability by raising the center of gravity and decreasing the metacentric height. When weight is added to a vessel, particularly above the designed limits, the center of gravity shifts upward. A higher center of gravity means that the vessel is less stable because it is more prone to tipping or listing when acted upon by forces such as wind or waves.

Additionally, the metacentric height, which is a measure of the initial stability of the vessel, decreases as the center of gravity rises. A lower metacentric height indicates that the vessel will have a shorter righting arm when it heels, resulting in less stability and a greater tendency to capsize under certain conditions. The combination of these factors underscores how excessive weight can adversely affect a vessel's ability to return to an upright position after being heeled over.

The other options present different notions about the effects of excessive weight; however, they do not accurately reflect the fundamental relationships between weight, center of gravity, and stability in maritime contexts.