USCG Assistant Engineer MODU (MODE02)

In a four-stroke-cycle diesel engine, how many crankshaft revolutions are required to complete one full cycle in each cylinder?

• AOne revolution (360°)
• BOne-half revolution (180°)
• CTwo revolutions (720°)
• DThree revolutions (1080°)

What is the primary purpose of fuel injection timing on a marine diesel engine?

• ATo control jacket cooling-water temperature
• BTo set the crank angle at which combustion begins so peak pressure occurs shortly after t…
• CTo regulate scavenge-air volume only
• DTo set lube-oil gallery pressure

The chief function of scavenging in a two-stroke diesel is to:

• AInject fuel at the correct crank angle
• BRemove burned gases from the cylinder and fill it with fresh air
• CCool the injector tip between firings
• DLubricate the wrist pin

A marine diesel governor primarily:

• ALimits maximum cylinder firing pressure by design only
• BAutomatically adjusts fuel rack position to maintain set speed under changing load
• CControls jacket-water thermostat setting
• DTimes exhaust-valve opening

Black smoke from a diesel exhaust under normal load most commonly indicates:

• AExcess lube oil burning in the combustion space
• BWater leaking into a cylinder
• CIncomplete combustion from excess fuel or insufficient air
• DNormal idle operation

What is the main purpose of a turbocharger on a marine diesel?

• ATo raise fuel pressure to the injectors
• BTo use exhaust energy to compress intake air and increase power output
• CTo cool exhaust before the silencer
• DTo dampen crankshaft torsional vibration

If starting air is applied but the engine will not turn and air pressure is normal, the most likely cause is that the:

• AExpansion tank is slightly low
• BTurning (jacking) gear is still engaged
• CDay-tank fuel viscosity is slightly high
• DCrankcase oil is slightly above the high mark

Jacket cooling water that is too cold during continuous operation can cause:

• AHigher thermal efficiency with no drawbacks
• BIncreased thermal stress and possible condensation of combustion products on liner walls
• CImmediate turbocharger overspeed only
• DAutomatic increase of injection timing

The primary purpose of the diesel engine lube-oil system is to:

• ACool only the turbocharger exhaust casing
• BLubricate and cool bearings and other friction surfaces while carrying away heat and cont…
• CProvide starting air to the cylinders
• DMeter fuel to the injectors

A sudden rise in lube-oil temperature with falling pressure on a main diesel most nearly indicates:

• ANormal warm-up after a cold start only
• BPossible bearing distress, thinning oil film, or restricted oil flow requiring immediate…
• CThat jacket-water temperature is too low
• DThat the fuel day tank is empty

On many medium-speed marine diesels, the purpose of a charge-air cooler (intercooler) is to:

• AHeat the intake air to reduce density
• BCool compressed charge air to increase density and improve combustion
• CSeparate water from fuel before injection
• DReduce lube-oil viscosity

Crankcase explosion risk on large diesels is reduced primarily by:

• ARunning with crankcase doors open for ventilation
• BMaintaining proper bearing clearances and oil mist detection, and never opening crankcase…
• CIncreasing injection timing advance indefinitely
• DBypassing the oil mist detector permanently

Starting-air manifold pressure on a diesel must be high enough to:

• ADrive the turbocharger at full load
• BOvercome compression and accelerate the engine to firing speed
• COperate the jacket-water pump only
• DPressurize the fuel day tank

A sticking fuel injector that dribbles can cause:

• AImproved atomization and lower exhaust temperature
• BAfterburning, local overheating, carbon deposits, and elevated exhaust temperature on tha…
• CImmediate loss of all jacket-water flow
• DAutomatic governor shutdown only with no combustion effect

Viscosity control of heavy fuel oil before injection is important because:

• AFuel viscosity has no effect on atomization
• BCorrect viscosity is required for proper atomization and injector protection
• CHigher viscosity always improves combustion at any temperature
• DViscosity only affects lube oil, not fuel

A diesel engine indicator card (pressure-volume or pressure-crank angle diagram) is used primarily to:

• AMeasure only lube-oil acidity
• BAssess combustion timing, peak pressure, and work developed in the cylinder
• CCalibrate the pyrometer scale alone
• DSet jacket-water chloride limits

If mean indicated pressure (MIP) is 12 bar and the engine geometry gives a constant K such that indicated power P_i = K × MIP × N, doubling speed N while MIP stays constant will:

• AHalve indicated power
• BDouble indicated power
• CLeave indicated power unchanged
• DQuadruple indicated power

The purpose of a diesel engine relief valve on a cylinder head (cylinder safety valve) is to:

• ARegulate fuel rack position
• BRelieve excessive cylinder pressure that could damage the engine
• CControl turbocharger wastegate only
• DBypass the governor

An oil mist detector alarm on a large diesel should be treated as:

• AA nuisance that can be ignored if oil pressure is normal
• BA serious indication of possible hot spots or bearing distress requiring load reduction a…
• CProof that the crankcase is free of mist
• DA signal to open all crankcase doors immediately while the engine is hot

Auxiliary diesel generators on a MODU primarily supply:

• AOnly emergency lighting permanently tied off the main bus with no generator
• BShip/unit electrical power for machinery, drilling support systems, hotel loads, and esse…
• COnly hydraulic pressure for BOP systems with no electrical output
• DStarting air only

A high exhaust temperature on one cylinder with others normal most nearly suggests:

• AUniform overfueling of all cylinders
• BA problem isolated to that cylinder such as injector fault, valve issue, or delayed combu…
• CJacket-water pump total failure
• DFuel day tank empty

The air cooler after a turbocharger compressor is fouled. The most likely result is:

• AHigher charge-air density and lower exhaust temperatures
• BHigher charge-air temperature, reduced density, higher exhaust temperatures, and possible…
• CLower turbocharger speed with richer mixture automatically corrected
• DImmediate loss of starting air pressure

What is the function of a fuel oil purifier (centrifugal separator) on a diesel installation?

• ATo raise fuel cetane number chemically
• BTo remove water and solid contaminants from fuel before the service system
• CTo cool jacket water
• DTo generate starting air

If a diesel is overloaded for a prolonged period, a common result is:

• ALower exhaust temperatures and cleaner combustion
• BElevated exhaust temperatures, smoke, and increased thermal and mechanical stress
• CAutomatic increase of turbocharger efficiency with no side effects
• DDecreased fuel consumption per power with no limit

A two-stroke marine diesel typically completes a power stroke:

• AEvery two crankshaft revolutions
• BEvery crankshaft revolution
• CEvery four crankshaft revolutions
• DOnly when the turbocharger is stopped

Cylinder liner lubrication on large crosshead diesels is important because:

• ALiners never require oil on the running surface
• BThe liner and piston rings need controlled oil feed for film strength while limiting exce…
• CLiner oil replaces the need for crankcase oil entirely
• DLiner oil is only used during starting air admission

A scavenge-space fire is most often associated with:

• AExcessive accumulation of oil and carbon deposits ignited by blow-by or hot spots
• BJacket-water temperature slightly below normal
• CA fully open crankcase relief valve as the root cause
• DLow starting-air pressure only

The term 'brake specific fuel consumption' (BSFC) expresses:

• AFuel used per unit of brake power output over time (e.g., g/kWh)
• BOnly the fuel tank volume
• CJacket-water flow rate
• DLube-oil TBN

An engine consumes 200 kg of fuel in 2 hours while developing 1,000 kW brake power. BSFC is approximately:

• A0.05 kg/kWh
• B0.10 kg/kWh
• C0.20 kg/kWh
• D0.40 kg/kWh

Before starting a diesel after major work, engaging the turning gear and barring the engine is done primarily to:

• APrime the turbocharger oil only
• BEnsure the engine is free to rotate and check for hydraulic lock or mechanical interferen…
• CSet the fuel rack to maximum
• DBypass all safety interlocks permanently

A drop in compression pressure on one cylinder of a diesel is most consistent with:

• AWorn rings, leaking valves, or liner wear on that cylinder
• BA completely empty lube-oil sump on a multi-cylinder engine with no other symptoms
• CNormal governor hunting only
• DA fully charged starting-air receiver

What does a wastegate or similar turbo control typically protect against?

• ALow charge-air pressure only as a desired outcome
• BExcessive turbocharger speed/boost that could damage the turbo or engine
• CJacket-water pump cavitation
• DFuel purifier bowl speed

On a MODU machinery plant, emergency diesel generators are typically arranged to:

• ARun only when the unit is in dry dock
• BAutomatically or manually supply essential electrical loads if main generation fails, per…
• CReplace the need for any fire pumps permanently
• DProvide propulsion thrust for transit only

Detonation or severe knock in a diesel is undesirable because it:

• AAlways improves thermal efficiency with no risk
• BProduces sharp pressure spikes that can damage pistons, rings, and bearings
• CCools the combustion chamber walls
• DReduces peak cylinder pressure safely

The jacket-water expansion tank on a closed cooling system primarily:

• AStores fuel for the day tanks
• BProvides a surge volume, allows air separation, and maintains a head on the system
• CPressurizes starting-air bottles
• DMeters cylinder oil to the liners

Oil-soaked insulation (lagging) on a hot exhaust manifold is a serious fire hazard mainly because:

• ALagging raises the exhaust gas temperature inside the pipe
• BAbsorbed oil is held in a thin layer against metal that can be hotter than the oil's igni…
• CWet lagging provides an electrical path from the manifold to the hull
• DLagging increases exhaust backpressure and overloads the turbocharger

Before releasing a fixed CO2 total-flooding system into a machinery space, the crew must:

• AKeep all ventilation running at maximum
• BEnsure personnel are evacuated, openings closed, and ventilation secured as required by t…
• COpen all doors to dilute the gas
• DSpray water into the space simultaneously to absorb CO2

The fire triangle components are:

• AFuel, heat (ignition source), and oxygen
• BFuel, nitrogen, and pressure only
• CHeat, light, and sound
• DCO2, foam, and water

Hydrogen sulfide (H2S) is especially dangerous offshore because it is:

• AAlways visible as a red cloud
• BHighly toxic, can deaden the sense of smell at higher concentrations, and is denser than…
• CHarmless below 1,000 ppm
• DLighter than air and never accumulates in pits

If H2S is detected at a level requiring evacuation of a machinery space, the correct general action is to:

• AIgnore alarms if you cannot smell anything
• BDon appropriate RPE if trained/required, evacuate upwind/to safe muster, account for pers…
• CShut yourself in the lowest bilge pocket
• DDisable gas detectors to silence alarms

Enclosed machinery-space entry requires, among other controls:

• ANo atmosphere testing if the space was recently occupied
• BPermit procedures, atmosphere testing, ventilation, attendant, and rescue plan as applica…
• COnly a verbal OK from any crewmember
• DOpen flame to test for gas

The normal safe oxygen concentration for unrestricted entry (approximate standard value taught in marine practice) is about:

• A5%
• B12%
• C16%
• D20.9% (near atmospheric)

Under MARPOL Annex I practice for machinery-space bilges, oily water may be discharged at sea only when, among other conditions, the oil content does not exceed:

• A100 ppm without monitoring
• B15 ppm through approved oily-water separating equipment with proper conditions met
• CAny concentration outside special areas
• D5% oil by volume

Machinery-space oily bilge operations and OWS use are recorded in the:

• AOfficial Log only with no oil record
• BOil Record Book (Part I for machinery space operations) as required
• CCargo Manifest exclusively
• DPassport of each engineer

OPA 90 primarily addresses:

• AInternational tonnage measurement only
• BU.S. oil pollution prevention, response planning, and liability after the Exxon Valdez era
• COnly recreational boat registration
• DSTCW rest-hour tables exclusively

Aqueous film-forming foam (AFFF) is most appropriate for:

• AClass D metal fires as the first choice always
• BClass B hydrocarbon fuel fires where foam is specified
• CEnergized high-voltage switchgear as the preferred agent
• DCombustible metal chips exclusively