Part B Engineering Flashcards
Oil drain plug has ______ to collect metallic filing in the oil
magnet
check oil level when it is:
a. hot
b. cold
b. cold before engine started
cylinders are located inside:
a. cylinder head
b. engine block
c. crankcase
b. engine block
inlet and exhaust valves are fitted in:
a. cylinder head
b. engine block
c. crankcase
a. cylinder head
crankshaft rotate within:
a. cylinder head
b. engine block
c. crankcase
c. crankcase
cylinder head gasket is placed between ___ and ___ to ensure gas and fluid tight.
a. cylinder head and engine block
b. engine block and crankcase
c. crankcase and cylinder head
a. cylinder head and engine block
torque wrench is for…
tightening screws or nuts with equal twisting force
what are the 4 strokes of 4 strokes engine?
- Induction
- Compression
- Expansion
- Exhaust
Both Petrol and Diesel engines can have 4 strokes mechanism, just the combustion sequence are different due to the different properties of petrol and diesel.
crankshaft rotates ___ times while camshaft rotates 360 degrees on a 4 stroke engine.
a. 360 degrees
b 720 degrees
720 degrees
crankshaft rotates twice as much as camshaft on 4 strokes engine.
valve clearance is ____ inches normally or refer to the engine manual.
0.025 inches
valve clearance is …
space located between rocker arm and valve stem to ensure valve closes fully for the engine.
if valve clearance is too small, valves cannot fully close and cause compression loss.
if valve clearance is too big, valves cannot fully open and cause noise (tapping noise).
in both cases the engine cannot run smoothly and lose power.
what is for adjusting valve clearance?
feeler gauge
bearings worn out symptioms
- knocking noise.
- lower oil pressure
- oil pressure gauge lower than 1000rpm
big-end bearing location
where connecting rod joins the crankshaft (bottom)
small-end bearing
where gudgeon pin joins the connecting road (top)
flywhel
to smooth the rotation of engine during explosion
stroke
the distance travelled by the piston between TDC (top dead centre) and BDC (bottom dead centre)
firing order of 4 cylinder 4 stroke engine
1, 3, 4, 2
compression ratio of petrol engine is x: y?
10:1 for petrol engine
compression ratio of diesel engine is x:y?
20:1 for diesel engine hence cylinder of piston of diesel is much longer
diesel or petrol has higher flash point?
diesel is 65C, petrol flash point is -44C and is much lower, and highly flammable.
when refueling, close…
all windows and doors
what will happen if diesel was put into petrol engine?
engine would stop or stop after starting
what will happen if petrol was put into diesel engine?
engine will be damaged due to over-speed if petrol was put into diesel engine.
before refuel boat:
- tied boat properly to fuel dock
- passengers have to stay ashore
- close windows and hatches
- ground the fuel nozzle to fuel filling point
- ready the foam type fire extinguisher
after using the boat, always fill up the tank or drain the tank to…
avoid condensed water (from air moisture) inside the tank and to prevent tank corrosion or engine stopping (fuel mixed with water).
what is choke for?
activate/ on the choke (choke plate closed) for cold engine starting to reduce air mixture with petrol to start the engine. turn off choke after starting the engine to avoid exhaust of uncombusted gas and smoky exhaust.
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The choke can be activated by a knob, button, or through a pull handle. When the choke is activated, its solenoid, a coil will expand and restrict the area through which air enters the carburetor.
what is a carburetor?
mixer of petrol and air - 50 petrol, 50% air.
ignition system turns 12v battery to x v at spark plugs for induction
20,000v +
contact break clearance is normally x to y mm/ inches
(ignition system)
contact break is normally 0.25 to 0.5mm (10-20/ 1000 inches). too wide > advance ignition; too narrow - retard ignition timing
what is a condenser (ignition) for?
connected to contact breaker to prevent sparks jumping across points of contact breaker. Thus protecting contact points from burning or pitting.
petrol engines are stopped by ….
cutter power (e.g. kill/ safety switch)
spark gap clearance is about ….
0.631-1.26mm (23-50/1000 inches)
spark occurs when contact breaker
a. opens
b. closes
a. opens
colour of spark plug nose grey - ? white - ? black - ? oily - ?
grey brown - normal
white - air-fuel mixture is too lean
black -air-fuel mixture is too rich
oily - lubrication oil burned inside the cylinder/ maybe scraper ring is gone/ need to replace piston.
cool plug and hot plug
cool plug (shorter) is for hot engines (e.g max 9k rpm); hot plug is for ool engines (e.g. max 4k rpm).
a set of plug, specified by engine manufacturer, should be kept onboard for spare.
lubricating oil and oil filter should be replaced regularly, at least ____
once a year to: reduce friction and wear reduce metal oxidation sealing, cushioning cooling cleaning
exhaust of blue smoke indicates
lubrication oil is burned in the cylinder
or
malfunction turbo charger (with engine lack of power, surge, knocking noise)
exhaust of white smoke indicates
water is burned in the cylinder
exhaust of black smoke
air fuel mixture is too rich/ not burned efficiently
or
faulty spring of diesel engine at injection
effective working temperature for the engine is normally around…
80-90C
sea water enter battery would cause the production of ___ gas
Chlorine gas - harmful to human beings
hydrometer is used to measure the specific gravity of the electrolyte indicating the state of charge of the battery
X = fully charged Y = half charged Z = discharged
- 28/ green - fully charged
- 2/ yellow - half charged
- 12/ red - discharged
main gauges on dashboard:
oil pressure gauge oil temp. gauge water temp. gauge exhaust temp gauge tachometer (RPM) Volt gauge/ meter
When there is a click click solenoid sounds when starting the engine, it indicates
low battery power, the battery need to be recharged
clearance between clutch plate and flywheel
too big clearance - slipping clutch > boat speed not correspond to engine speed
too tight clearance - lug clutch > propeller running while neutral gear
zinc is fitted underwater to protect submerged metals from galvanic corrosion
do not pain on the zinc
thrust bearing is for ….
withstanding axial movement of the propeller shaft and keep other parts of the engine e.g. crankshaft in place
larger pitch propeller bigger angel of blade give a ____ top-end speed.
a. higher
b. lower
higher
speed boat uses large pitch propeller
cruiser uses small-pitch propeller
if engine speed is unchanged but vessel speed is reduced significantly, the propeller may be ______
fouled by obstruction. best way is to go neutral to avoid the fouling.
diesel fuel pressure is increased to ____ bar/ psi + in the injector pump before fuel is injected into the piston of a diesel engine
70 bar/ 1000 psi
diesel engine is stopped by cutting _____
fuel
adjusting the angel of helical edge wll adjust the connection between spill port and helical edge end up controlling the quantity of _____
quantity of diesel fuel delivered to fuel injector and thus control the engine speed
diesel engine - what is a governor
mechanical auto device which reduce the fuel supply if engine is over-speeding (e.g when propeller comes out of water), thus protecting the engine from damage. also adjust idle and max engine speed.
diesel engine - decompressor
for engine cranking and starting. do not use it for engine stopping or fuel may leak into exhaust pipe and cause fire.
diesel engine - low voltage glow plug
is an air preheating device, locate at the top of combustion chamber, or intake manifold for cold engine starting
2 stroke engine is more/ less powerful than 4 strokes engine?
2 stroke engine more powerful
reed valve/ leaf valve
non return valve - goes only one way to draw air fuel mixture in cylinder
2 stroke engine camshaft spin 360 degrees, crank shaft spins x degrees
360
scavenge
exhaust gases forced out of the cylinder by fresh air compressed in by blower (diesel engine)/ transfer port (petrol engine)
dingy has around x to y h/p diesel/ petrol engine?
2.2-8hp petrol engine
lubrication for 2 stroke outboard engine
lub oil is mixed with petrol and mixture ratio is around 50:1 (petrol: lub oil)
to remove blockage at propeller
- reduce throttle
- idle engine
- reverse gear
- one throttle
idle outboard engine should be placed in proper position to avoid fuel spillage from carburettor or cooling water residue entering engine cylinder. always keep the engine with pistons higher/ lower than propeller or carburettor face upward/ downward
pistons higher than propeller
or
carburettor face upward
procedure to stat an outboard engine
- lower the leg of the engine and tighten it up
- pump fuel to carburettor or turn on fuel cock
- shift gear to neutral
- open the choke (if cold).
- open 1/4 of throttle (ready position for starting)
- pull the manual (rope) starter
- check cooling indicator
when underway, the leg of outboard motor should be at ___ degrees to the water surface & propeller shaft should be ___ degrees to the water surface
90 degrees/ right angle
180 / parallel
difference between 4 stroke petrol & diesel engine
Ignition point: P - 44c; D - 65c
ignited by: P - spark; D - compressed hot air
Compression ratio: P - 10:1; D - 20:1
Draw in: P - air-fuel mixture; D - air
Weight: P - lighter; D - heavier
Noise: P - less noisy and steady; D - nosier and vibrant
Running cost: Po higher; D - lower
difference between 4 stroke & 4 stroke petrol engine
crankshaft rotation: 2 - crankshaft 360degree = 1 power stroke; 4 - crankshaft 720 degrees = 1 power stroke
camshaft - 2 stroke - no camshaft (as no valves)
2 stroke has reed valve at crankcase; 4 stroke has inlet valve at cylinder head
2 stroke has gas tight crankcase; 4 stroke has non gas tight crankcase
2 stroke has lub oil mixed with fuel; 4 stroke has isolated lub system;
2 stroke is ligher and structure is more simple
2 stroke consumes more fuel
bigger vessel should be fitted with an oily water separator in the bilge pump system to prevent oil pollution the waters. what is bigger vessel?
22m long vessel / registered gross tonnage 400+
Foam Fire Extinguisher is usually used for fire in ____
engine room
do not use ____ fire extinguisher for class b fire - flammable liquids, like oil, petroleum etc.
water fire extinguisher not for flammable liquids
CO2 and Halon gas are harmful to human body
Halon gas (aka BCF and BTM) are high efficient fire fighting aent, but harmful to human being environment
turn off ____ in case of electrical fire
power
turn boat to ____ side if bow was on fire, but head on ____ if stern was burning
turn boat to leeward if bow on fire
turn head on wind if stern was burning
Fire fighting procedure
f- find
i- inform
r- restrick
e- extinguish
foam fire extinguisher
do not spray directly to source of fire, spray around it
Co2 fire extinguisher usage
spray gas to surround fire
dry powder
directly spray to base of fire, sweep fromside to side until the whole flame is covered.
