A diesel engine with a full speed of 900 RPM drives a propeller at 300 RPM. What is the speed reduction ratio?

To determine the speed reduction ratio of the diesel engine to the propeller, you take the full speed of the engine and divide it by the speed of the propeller. In this case, the diesel engine operates at 900 RPM, while the propeller operates at 300 RPM.

Using the formula for speed reduction ratio:

Speed Reduction Ratio = Engine Speed / Propeller Speed

Substituting in the values:

Speed Reduction Ratio = 900 RPM / 300 RPM = 3

This means that the engine spins three times faster than the propeller. Therefore, the correct speed reduction ratio is 3:1. Understanding this concept is crucial for engine operation and maintenance, as it helps engineers gauge the performance and efficiency of propulsion systems in marine applications.