Coast Guard Exams
Question 30Motor Plants - 1st Asst/Chief70% to pass

If the speed of the propeller is 135 RPM, the speed of the engine camshaft shown in the illustration will be_______________. Illustration MO-0003

Diagram for question 30
AI Explanation
The correct answer is A) 135 RPM. In a marine engine, the speed of the camshaft is directly linked to the speed of the crankshaft, which in turn is directly linked to the speed of the propeller. Since the propeller speed is given as 135 RPM, the speed of the engine camshaft will also be 135 RPM, as they are directly connected through the engine's internal gearing. The other options are incorrect because B) 270 RPM would be twice the propeller speed, which is not the case, and C) and D) suggest the camshaft speed could be variable, when in fact it is directly proportional to the propeller speed in a fixed gear ratio.