Propulsion and Machinery Systems Flashcards
7 cards from real SAMS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Propulsion and Machinery Systems flashcards as text
When inspecting a vessel's reduction gear, a marine surveyor notices pitting on gear teeth. What does this typically indicate?
Answer: Lubrication failure or contaminated gear oil
Pitting on gear teeth is a classic sign of lubrication failure or oil contamination, which prevents proper film formation between meshing surfaces.
A diesel engine's turbocharger is producing an audible whine at elevated RPM. What should a surveyor check first?
Answer: Turbine and compressor blade condition and bearing wear
An abnormal whine from a turbocharger typically indicates worn bearings or damaged blades in the turbine or compressor section.
What is the primary purpose of a shaft seal (stuffing box or lip seal) in a propulsion system?
Answer: To prevent seawater ingress into the vessel around the propeller shaft
A shaft seal prevents seawater from entering the vessel through the aperture where the propeller shaft penetrates the hull.
During a sea trial, a surveyor observes that engine RPM drops when the vessel turns to starboard. This symptom most likely indicates:
Answer: Propeller cavitation or shaft misalignment exacerbated by hull loading in turns
RPM drop during turns often suggests propeller cavitation or shaft/strut misalignment that worsens when hull attitude changes in a turn.
What does a high exhaust back pressure reading indicate in a marine diesel engine installation?
Answer: A restriction in the exhaust system such as a blocked muffler or collapsed hose
Elevated exhaust back pressure points to a restriction downstream of the engine, commonly a blocked wet muffler, kinked hose, or collapsed exhaust riser.
A surveyor finds bronze through-hull fittings adjacent to the aluminum stern drive. What corrosion concern should be documented?
Answer: Galvanic corrosion due to dissimilar metals in an electrolyte
Bronze (copper alloy) and aluminum are far apart on the galvanic series; when coupled in seawater, the aluminum will sacrificially corrode rapidly.
Which condition would a surveyor most expect to find associated with a cavitating propeller?
Answer: Erosion pitting on the suction face of the blades near the tips
Cavitation causes vapor bubbles to implode violently against blade surfaces, leaving characteristic erosion pits primarily on the suction face near blade tips.