Final answer:
The length of non motorized vessels cannot be determined without additional context as they can vary widely. In the context of a math textbook chapter on Customary Lengths, the focus is on the techniques of measuring and estimating different lengths.
Step-by-step explanation:
The length of non motorized vessels can vary greatly; they can be less than 16 feet, exactly 16 feet, or more than 16 feet in length. However, without additional context, we cannot determine the specific length of a non motorized vessel. The length depends on the type and purpose of the vessel, the design, and other factors that influence the vessels dimensions. For educational purposes, like in the chapter regarding Customary Lengths from a math textbook, the focus would be on teaching students how to measure, estimate, and compare different lengths, rather than providing specific dimensions for types of vessels.