Engineering Flashcards
What is a seacock?
water inlet for the water pump
Purpose of oil sump
collect and cool oil collect collect and cool oil
Crankcase
House for the crankshaft
Cooling circuit
Green Square - Water, Red Circle - Oil
Signs of burnt head gasket
Running engine to hot, Oil stains, bubbling cooling water tank, EMULSION (higher reading on dipstick due to water in oil sump)
Torque Wrench
Tighten screws/nuts with equal force ACCORDING TO SPECIFICATION OF THE ENGINE
Blue Smoke
Oil entering compression chamber
White Smoke
Water entering compression chamber
List Items connected to Cam Shaft
1.
2.
3.
4.
5.
- Cam Shaft
- Cam
- Push rod
- Valve Spring - (USED TO CLOSE THE VALVE)
- Rocker Arm
Timing Gears & chain?
Ratio Crankshaft : Camshaft in a 4 stroke engine
Used to transfer rotation of crankshaft to camshaft which moves push rods and rocker arms to OPEN the valves
SPRING - Closes the valves
2:1
Where is the Tappet valve (Cam follower) located
Between the cam and the push rod
What does rocker arm do?
What does valve spring do?
Rocker Arm - Opens the Valve
Spring - Closes the valve
Valve clearance
Located between rocker arm and valve STEM which ensures VALVE CLOSES FULLY AFTER ENGINE WARMS UP
0.025 inches in the normal clearance OR REFER TO ENGINE MANUAL
Which valve normally has a larger diameter
INTAKE
What happens if the valve clearance is to small after the engine warms up?
Valve wont close properly leading to engine COMPRESSION LOSS
Engine wont run smoothly
What happens if the valve clearance is to BIG after the engine warms up?
Valve become NOISY - TAPPING SOUND
Engine wont run smoothly
What does Feeler gauge tool do?
Hand tool for adjusting valve clearance
Gudgeon Pin?
Connects piston to the con rod
Big end bearing?
Small end bearing?
Con rods join the crankshaft
Gugdgeon pin joins the con rod
Main Bearing?
Symtoms of warn out bearing?
Supports crankshaft on the engine block
knocking noise and low engine oil pressure in a running engine
Engine speed?
Number of rotations equivalent to the rotation of the crankshaft
Flywheel
Stores engery during expansion and releases it during the other 3 three strokes to make the engine run SMOOTHLY
Stroke
Distance travelled between TDC and BDC
1 stroke - Camshaft turns 180 degrees (4 stroke engine 720 degrees)
2:1 ratio
Power stroke Piston movement
CLOSE TO TDC, spark which ignites fue/air
4 stroke engine 1000rpm - calculation of power strokes?
1000/2 = 500 power strokes X no. of cyliners =
Valve timing - Overlap
Both valves open together in order to clear the exhaust gases completely from the cyliner
Lead (Advance) - Valve
Lag (Retard) - Valve
Valve opens before TDC or BDC
Valve opens after TDC or BDC
Firing order of Pistons
1,3,4,2
Induction
Compression
Expansion
Exhuast
What is timing light gun used for
Checking ignition timing
Petrol engine compression ratio?
Diesel engine compression ratio?
Calculate the above?
10: 1
20: 1
Piston working volume (X) + Clearance Volume (Y) = Clearnance Volume (Y)
Red diesel fuel
Dye fuel - cheaper due to lower tax, intended for industrial use
Density/Flashpoint Petrol?
Density/flashpoint Diesel?
-44 degrees / 0.73g
+65 degrees / 0.84g
Safety when refueling
Close all windows and doors
Diesel fuel in petrol Engine?
Petrol in Diesel Engine?
PRETOL ENGINE WILL STOP AFTER STARTING
OVERSPEED DIESEL ENGINE
What operates the fuel pump?
Camshaft
STEPS before reufing boat
1.
2.
3.
4.
5.
- TIED
- Passengers ashore
- CLOSE windows/doors
- GROUND fuel nozzle
- READY FOAM extinguisher
3 purposes of Air filter
- Clean
- Silencer
- Flame trap
Needle Valve
Float chamber of the Carb, cuts off fuel supply
Pilot Jets
Main Jet - Fast Speed
Slow Jet - Idle speed
Mixture control screw
operate 1/4 of the throttle for 10 minuts to warm up the engine
Mixture in the carb
Normal operation?
Flooded?
Petrol/Air?
50: 50
80: 20
60: 40
Causes of Engine flooding
Needle valve not closing
Can’t start engine because mixture is to rich
temp fix - turn off fuel from tank and crank the cylinders dry
Choke plate closed
Richens mixture for cold starting
- Choke
- Main Jet
- Throttle Valve
- Slow speed Jet
- Float
- Needle Valve
B - Fastmmoving air
A/C - Slow moving Air
LEAN MIXTURE symtoms/causes
Leaking intake manifold, wrong adjustment
WHITE spark plug
pre ignition
cyliner knocking
engine vibration and lack of power
RICH MIXTURE symtoms/causes
Wong adjustment,dirty air filter, fuel flooding engine, OVERLOADING engine
Black emmisions
Black colour spark plug tip
Engine stop after warm up
Carbon buit up in the exhaust manifold
Igntion - Lobbed cam?
Operates contact breaker (open/close)
Distribuor /cam shaft ratio
4 stroke -
2 stroke -
4 stroke - 1 : 0.5 (half speed)
2 stroke - 1 : 1
Induction Coil?
Primary and secondary windings - 12v to 20 000v
High voltage jumps the gap on the spark plug to which makes a spark
Contact Breaker
Connected to primary windings, when it opens high voltage is produced in the secondary windings
CLEARANCE CONTACT BREAKER - 0.25mm - 0.50mm (10-20/1000 inches)
Purpose of the condensor?
Connecting to the contact beaker to prevent sparks from jumping across the contact breaker, thus protecting CONTACT POINT
Distributor shaft speed?
Driven by the Camshaft at HALF the engine speed
enables firing order 1,3,4,2
A,B,C,D,F - HIGH Voltage
I,E,H,H - Low voltage
- Lobed Cam
- Battery
- Rotor Arm
- Contact breaker
- Condenser
- Induction coil
Spark plug gap clearance
0.63 - 1.26mm (25-50/1000 inches)
Sprak plug gap to large
Use FEELER GAUGE to adjsut earth electrode
Spark plug colours
Grey
White
Balck
Oily
- Engine running normally
- Mixture to lean
- Mixture to rich
- Engine needs to be overhauled
HOT ENGINE (9000rpm) - What type of plug?
COLD ENGINE (4000 rpm) - What type of Plug?
OPPOSITE!!
HOT - Cold plug (Shorter)
COLD - Hot plug (Longer)
What Spare should be kept on the boat?
SPARK PLUGs
Oil pump speed
Half the speed on a 4 stroke engine
When do you check oil levels?
Engine is cold - Always topup oil with the same oil type
Sea water cooling (Direct cooling system)
Wet exhaust (with rubber tubing)
IMPRELLER (plastic pump)
Fresh water cooling system( Indirect cooling system)
Heat exchanger (sea water cools fresh water which is circulated)
CENTRIFUGAL PUMP (metal)
Direct Cooling
Sea water, less efficient due to salt
Thermostat enabes engine to warm up quickly
Thermostat stuck open - engine will take longer to warm up
Stuck closed - Engine will overheat
Indirect cooling
Sea water through heat exchanger
BRONZA seacock - must be turned on before starting and turned off after shutdown
More efficient and less corrosion in the engine, coolant is deeivered more evenly inside the circuit
Fresh water pump driven by the engine V-belt
Common causes of engine overheating
Sea cock blocked up
heat exchanger dirty or cooling ccircuit blocked
water pump (impellor or V-blet broken)
Stuck thermostat
running engine slowly for to long
What do you do if your engine overheats?
DO NOT SWTICH IT OFF - Run it at idle
Swan neck pipe?
loop pipe to ensure seawater does not travel up the exhaust and into the engine
Advantages/Disadvantages of wet exhaust pipe (Rubber)
Rubber hose
lowers engine noise, exhaust pipe temp, lower risk of fire.
Corrosion, cooling water leaking into bilge causing low water pressure in the system, water entering engine cylinders damaging them
12v battery formed?
6 units of 2volt celss are connected in series to form 12v
Specific Gravity of batterys
Discharged?
Half charged?
Fully charged?
- 12
- 2
- 28
Alternator…..
Use same rating fuse for replacement or install a circuit breaker for the electrical system
Output unit of a generator is measured in KW
When battery is low, running generaotr will power the ignition and electrical system
what do you do if a generator overspeeds?
Turn it off!!
First thing you do when connecting to shore power?
Turn off the main switch and the power supply of the boat!
Earth lamp (ground lamp)
Lights equal color - circut is healthly
Logihts not equal colour - problem with insulation or circuit grounded and should be check or rectified
Starter - What happens when battery power is turned on?
Solenoid connection Pinion (small wheel) to the flywheel teath - Starter motor driver flywheel and crankshaft
What wiring should you connect to the starter?
Short thick wiring for maximum current
Purpose of gearbox?
Reduce prop shaft speed increasing thrust (torque)
How is gearbox cooled?
By WATER to maintain proper viscosity
Thrust Bearing?
Withstand the axial movement of the propeller shaft
Coupling?
System connector, alignment adjuster, shock absorber for the prop shaft
Sterntube?
Located under the engine and goes through the bottom of the hull, holds prop shaft which rotates inside it adn prevents the engine room from flooding
Gland???
Loosen when the boat is running, tighen when the boat is not in use
Zinc??
Saccrificial zinc is fitted underwater as to protect the submerged metals from galvanic corrosion
what type of prop gives higher top end speed/Low speed?
Large pitch with bigger blade - Fast (speed boat)
Small pitch prop with smaller blade - Slow (junk boat)
What if engine speed is unchanged but vessel speed reduces?
Floating rope ahead of the vessel in the water?
prop may be fouled by obstruction
Reduce engine speed to neutral
Difference between Diesel and petrol ignition?
Petrol - Spark Plug
Diesel - High temp air
Rubber Hose Diesel engine?
Low pressure fuel back to the tank
What increases diesel fuel pressure?
Injector pump (1000 psi)
When will Diesel engine stop?
Air is present in the fuel system - You have to bleed the system
Diesel engine - plunger is down/up?
Diesel flows from the inlet port - DOWN
No fuel flows - UP
How to control throttle diesel engine?
HELICAL EDGE plunger adjsuts the timing of the connection between the spill port and helical egdge. This controls teh quantity of diesel fuel delivered to tthe fuel injector, thus controlling engine speed
What does the spring on diesel engine do?
When diesel pressure is greater than pre set spring pressure, needle valve opens and diesel fuel sprays through tiny holes at the nozzle to the cylinder
Special features in DIESEL engine only?
1.
2.
3.
- Governor - reduces fuel supply if engine overspeeds
- Decompressor - easy cranking and starting (manual valve opener/manual vacuum releaser)
DO NOT USE IT FOR ENGINE STOPPING or fuel may leak into the exhuast pipe and cause fire
- Low voltage glow plug - device to preheat air, located at the top of the combustion chamber or intake manifold
turbocharger - Damaged intercooler (heat exchanger)
Casue engine lack power, surge, KNOCKING NOISE and cylinder temp to overheat
Signs of a mulfucntioning turbocharger
KNOCKING NOISE with BLUE EXHAUST smoke, lack of engine power
Bypass valve do on hydraulic steering?
prevents hoses from bursting
What if the rudder angle gauge is out?
Check rudder stock and bearing should be checked adn rectified
Defintion of confined space?
What to do before entering confiend space?
Only one entrance and exit - only certified persons may be allowed to work inside
- Suggicient lighting
- Good ventilation
- No existance of pousonous or flammable gases
Watcher to be at the entrance of a confined space
What does the reed valve do in a 2 stroke piston engine?
Air-Fuel mixture is transferred into the crankcase through the REED valve
Transfer Port 2 stroke engine?
Compressed air/fuel mixture in the crankcase is transferred under pressure to the cylinder through the TRANSFER PORT as the piston moves down
2 stroke power calculation?
2:1
1000rpm/2 = 500
2 stroke Diesel crankshaft : Camshaft ratio?
1 : 1
What does Blower do?
Air compressed in cylinder bny the blower on 2 stroke diesel engine
What is scavenging on 2 stroke diesel engine?
Exhaust gases are futher forced out when the piston is at BDC by fresh compressed air from the blower
revolutions on a 100 000 HP diesel 2 stroke engine?
50 - 100 rpm - SLOW REVOLUTION ENGINE
Outboard engine - Ignition?
Magneto under the flywheel, replaces the battery
Mixture ratio of 2 stroke oil fuel?
50 :1
Outboard engine - Cooling?
Direct cooling by seawater, discharged through prop hub abd exhaust
STEADY STREAM of discharging water as an indicator for the proper function of the cooling system
Outboard engine - Transmission system?
Bevel gears and a dog clutch. transmission oil should be filled in from the OIL HOLES at the gearbox casing which is located in the leg of an outboard motor
Shear Pin/Rubber Bellow?
Metal pin installed on the prop hub to prop shaft and will break on impact, protects the engine, RUBBER BELLOW serves the same purpose on big horse outboard engines
How to place an outboard engine to avoid fuel spillage from the carb?
PISTONS HIGHER than prop // CARB FACING UPWARDS
Procedure to start outboard engine
- lower leg of the engine and TIGHTEN
- Pump fuel to carb
- Shift gears to neutral
- Open the choke
- Open 1/4 of the throttle
- Pull manual rope starter
- Check cooling indicator
position of outboard engine underway?
leg of the outboard should be at right angles to water surface, prop shaft PARALLEL/180 degrees
Stem out engine overheating ***
- Move out of channel
- Reduce to idle speed, DONT STOP ENGINE
Does a 2 stroke or 4 stroke engine have a gas tight crankcase?
2 stroke engine only!!!!
Distance between pump and sea level for manual bilge pump?
7m (due to atmospjeric pressure limitation)
What vessels should be fitted with an oily water seperator int he bilge pump system?
Vessel gross weight over 400 tonnes
Where should you store LPG gas cylinders on board?
Full or empty, kept in a lockable compartment having gas tight boundries with the hull
What material should a long length gas tube be made of?
Metal, only ends should be rubber
In case LPG gas escapes?
Vigorous flapping of blanket, large towel or canvas will assist in diffusing gas in air via opened windows and doors, soapy water can be used to locate a gas leak
How often does LPG gas cyclinder require to be pressure tested?
5 years
check co2 fire extinguishe for leak?
weight, looses more than 10% replace it
What fire extinguisher is hazardeous to humans in a confined space?
CO2 and HALON
what happens in LPG leak is drawn into running cylinders?
SPEED UP engine
How do fires spread?
Conduction, convection, radiation
what information does the exhuast temp reading provide you?
Engine loading
volt meter range?
12.5v - 15v
Causes of excessive engine vibration
Sterntube bearing/prop shaft bearing worn out, valve vlearance needed to be adjsuted or transmission system problem
Manual Bilge Pump - Distance between pump and sea level?
Limited to 7m due to atmospheric pressure
Manual Bilge Pump - Made of what?
SOLID and RIGID material
4 types manual bilge pumps
Diapham - HIGHER DISCHARGE CAPACITY, DOES NOT CLOG
Piston Pump - LOWER DISCHRGE CAPACITY, CLOGS
Semi Rotarty Pump - PRIMING REQUIRED
Piston Pump (to and For type)
