MTC Marine Technician Engine Systems 2 — Questions and Answers
Question 1: What is the purpose of a marine engine's raw water strainer?
- To filter debris before water enters the cooling system (Correct answer)
- To regulate water pressure to the impeller
- To separate fuel from bilge water
- To cool the exhaust manifold directly
Correct answer: To filter debris before water enters the cooling system
The raw water strainer removes debris and particulates from seawater before it reaches the impeller and cooling circuit.
Question 2: A four-stroke inboard diesel engine fires on which stroke?
- Intake stroke
- Compression stroke
- Power stroke (Correct answer)
- Exhaust stroke
Correct answer: Power stroke
Combustion occurs at the top of the compression stroke and drives the piston down during the power (expansion) stroke.
Question 3: Which component in a marine diesel injection system controls the precise timing and quantity of fuel delivery?
- Lift pump
- Injection pump (Correct answer)
- Day tank
- Fuel polisher
Correct answer: Injection pump
The injection pump meters and pressurizes fuel, delivering it to injectors at the correct timing and quantity for each cylinder.
Question 4: When inspecting a flexible engine mount, which condition warrants immediate replacement?
- Minor surface discoloration
- Rubber bonded to metal showing cracks or separation (Correct answer)
- Slight oil residue on the mount base
- Paint peeling from the mount bracket
Correct answer: Rubber bonded to metal showing cracks or separation
Cracks or separation in the rubber-to-metal bond indicate the mount has failed its isolating function and can allow damaging vibration or engine misalignment.
Question 5: What does a high exhaust back pressure reading indicate on a marine engine?
- Over-fueling condition
- Restriction in the exhaust system (Correct answer)
- Low cylinder compression
- Excessive valve clearance
Correct answer: Restriction in the exhaust system
Elevated back pressure indicates a blockage or restriction—such as a clogged muffler or collapsed hose—that impedes exhaust gas flow.
Question 6: A marine technician notices white smoke from a diesel engine at startup that clears after warm-up. What is the most likely cause?
- Worn piston rings
- Normal combustion of condensed moisture and unburned fuel during cold start (Correct answer)
- Head gasket failure
- Cracked exhaust manifold
Correct answer: Normal combustion of condensed moisture and unburned fuel during cold start
White smoke on a cold diesel start is typically condensed water vapor and lightly unburned fuel that dissipates once the engine reaches operating temperature.
Question 7: What is the function of the thermostat in a freshwater-cooled marine engine?
- Regulate raw water flow rate
- Maintain consistent engine operating temperature by controlling coolant circulation (Correct answer)
- Prevent corrosion in the heat exchanger
- Control fuel delivery based on temperature
Correct answer: Maintain consistent engine operating temperature by controlling coolant circulation
The thermostat restricts coolant flow until the engine reaches its designed operating temperature, then opens to allow full circulation through the heat exchanger.
MTC Marine Technician Engine Systems 2
What is the purpose of a marine engine's raw water strainer?