Selusuh

Selusuh is a traditional Indonesian speedometer, typically used in boats and ships. Its primary function is to measure the rotation speed of the vessel's propeller, providing the crew with essential information about the vessel's speed and performance.

The term "selusuh" is derived from the Indonesian language, with "selu" meaning to count or measure and "suh" implying speed. This simple, yet effective instrument has been used for centuries by Indonesian sailors and fishermen, predating modern electronic speedometers.

Selusuh usually consists of a rotating dial with graduated markings, attached to the external housing, which contains the numerical display of the vessel's speed. By attaching the selusuh to the boat's propeller shaft or a rotating shaft connected to the propeller hub, the instrument directly measures the propeller's rotational speed, taking into account the gear ratio to derive the actual boat speed.

While selusuh has largely been replaced by modern electronic speedometers in modern vessels, it remains an important tool in traditional Indonesian boat-building and sailing practices. The instrument's reliability and simplicity in operation have also led to its adoption in some unique applications, such as invertebrate performance measurement in oceanographic research.

The design and functionality of selusuh have undergone minimal changes since its inception. Its relatively simple construction has allowed it to evolve over time, making it an important example of traditional Indonesian marine innovation. The selection and assembly of selusuh remain a responsibility of skilled boat craftsmen and marine technicians in many Indonesian coastal communities.