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
What does the term 'propeller slip' refer to in marine propulsion?
Answer: The difference between theoretical and actual advance per revolution
Propeller slip is the difference between the theoretical pitch distance the propeller should advance per revolution and the actual distance traveled through the water.
A surveyor notes that a vessel's inboard engine raw water cooling pump impeller is made of nitrile rubber. What inspection finding would indicate impeller failure is imminent?
Answer: Vanes show set (permanent curve), cracking, or missing pieces
A nitrile impeller with permanent vane set, cracks, or missing pieces is near failure and will rapidly cause engine overheating if not replaced.
When evaluating a vessel with twin diesel engines and a common seawater intake manifold, what specific risk should a surveyor note?
Answer: Cross-flooding or loss of cooling water to both engines if the shared intake seacock fails
A shared seawater intake means a single seacock failure can simultaneously deprive both engines of cooling water, an important redundancy risk.
What is the function of a cutless bearing in a propulsion system?
Answer: To support and center the propeller shaft at the strut or stern tube using water lubrication
A cutless bearing is a rubber-lined, water-lubricated bearing that supports the propeller shaft at the strut and maintains shaft alignment.
A surveyor observes that a marine gas turbine vessel has an intake plenum with visible salt crystal deposits. What operational problem does this indicate?
Answer: Failure of the intake air filtration and washing system
Salt deposits in the intake plenum indicate the air filtration or anti-icing/wash system has failed, allowing corrosive salt-laden air to reach the compressor.
When surveying an outboard motor on a fiberglass transom, what structural condition is most critical to evaluate?
Answer: Transom core delamination or saturation that reduces motor mounting strength
A delaminated or water-saturated transom core loses structural integrity, which can cause motor bracket failure and motor loss under load.
What reading would alert a surveyor to excessive crankshaft main bearing wear on a running diesel engine?
Answer: Abnormally low engine oil pressure at operating temperature and RPM
Worn main bearings increase bearing clearances, allowing oil to escape faster and reducing oil pressure measured at the sender.