Marine Technician Engine Systems Flashcards
7 cards from real MTC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Marine Technician Engine Systems flashcards as text
A marine technician performs a cylinder leak-down test and finds 40% leakage with air escaping from the crankcase breather. What does this indicate?
Answer: Worn piston rings allowing combustion air past the piston
Air escaping into the crankcase during a leak-down test indicates piston rings are not sealing, allowing pressurized air to blow past the piston.
When aligning a shaft coupling on a direct-drive inboard installation, what is the preferred tolerance for angular and parallel misalignment?
Answer: As close to zero as possible, typically within 0.003–0.005 inch
Shaft coupling alignment should be within manufacturer specs, typically 0.003–0.005 inch for both parallel and angular misalignment, to prevent vibration and bearing damage.
What is the function of an intercooler (charge air cooler) on a turbocharged marine diesel?
Answer: Cool compressed intake air to increase air density and improve combustion efficiency
An intercooler cools the heated compressed air from the turbocharger, increasing its density so more oxygen enters the cylinder, improving power output and efficiency.
During a sea trial, a twin-engine vessel pulls noticeably to one side at cruise speed. Which engine system issue should the technician investigate first?
Answer: Mismatched engine RPM or propeller pitch between the two engines
A thrust imbalance caused by RPM mismatch or propeller pitch difference is the most common cause of unintended tracking deviation on twin-engine vessels.
What is the purpose of a marine engine's blow-by measurement?
Answer: Quantify combustion gas leaking past piston rings into the crankcase to assess engine wear
Blow-by testing measures the volume of combustion gases entering the crankcase, which indicates piston ring and cylinder wall wear.
A marine diesel runs rough and produces black smoke under load. Which condition is most consistent with these symptoms?
Answer: Over-fueling from a stuck open injector or faulty injection pump
Black smoke indicates unburned fuel, characteristic of over-fueling caused by a faulty injector delivering too much fuel or poor atomization.
Which measurement determines if a marine diesel cylinder bore requires reconditioning?
Answer: Bore diameter measured at multiple depths and orientations to detect taper and out-of-round
Measuring bore diameter at top, middle, and bottom in both parallel and perpendicular planes reveals taper and out-of-round wear that determines if boring is needed.