MAINTENANCE EXERCISE: QUESTIONS ONE NAME:

1. Mechanical interlocks prevent an outboard being started while the gears are engaged. Why are these interlocks are provided?
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2. A new outboard engine shows no cooling water ‘tell-tale’ when it is first started. What action should you take?

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3. An outboard engine fails to start. List the first things you would quickly check before removing any engine components.

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4. List the problems that a thorough cleaning and inspection of an outboard engine might reveal before going to sea.

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5. Make a list of possible symptoms in any type of marine engine which could warn you that there is an engine problem!

a)_____________________________________________________

b)_____________________________________________________

c)_____________________________________________________

d)____________________________________________________

e)_____________________________________________________

f)_____________________________________________________

g)_____________________________________________________

MAINTENANCE ANSWERS ONE

1.Mechanical interlocks prevent an outboard being started while the gears are engaged. Why are these interlocks are provided?
For safety, for example to prevent a lightweight vessel accelerating away, possibly dumping the crew overboard, and to prevent another person holding the vessel being struck by the propelle.r

2. A new outboard engine shows no cooling water ‘tell-tale’ when it is first started. What action should you take?
Stop the engine immediately and investigate to find out if a thermostat is fitted or if the cooling system is faulty.

3. An outboard engine fails to start. List the first things you would quickly check before removing any engine components.
Check that any emergency stop switch/safety lanyard is set to’ run’ position.
Check that the gears are set to Neutral
Check that the fuel tank has sufficient fuel, the fuel tap (if fitted) is ‘on’, the fuel line is connected, and the engine is primed using the priming bulb.
Check that the correct engine cold start procedure is being used.

4. List the problems that a thorough cleaning and inspection of an outboard engine might reveal before going to sea.
Loose, damaged or missing parts
Cracked or damaged fuel lines
Cracked electrical insulation and corroded wiring
Cracked or damaged propeller and damaged drive bush or pin
Badly corroded or ineffective anodic place.

5. Make a list of possible symptoms in any type of marine engine which could warn you that there is an engine problem!

a) Engine won’t crank over.

b) Engine cranks but fails to start

c) Engine runs, but misfires or delivers reduced power

d) Blue, black, or white smoke present in the exhaust

e) Unusual noises from the engine

f) Lubrication or cooling system problems

g) Others ?

h) .......................................................................................................

i) .......................................................................................................

j) .......................................................................................................

MAINTENANCE QUESTIONS TWO

1. How can you quickly find out if a starting problem is being caused by a flat battery?

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2.         The engine cranks but won’t start. Show the order you would use to check the system out, by numbering from 1 to 4, the statements below:
.......     Remove and replace starting aids
.......     Check filters
.......     Check fuel level and fuel cock
.......     Undo the fuel line at the fuel pump outlet and check the flow

3. The diesel engine starts, but runs poorly and produces black smoke from the exhaust. What is the most likely cause of the problem?

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4. The engine starts running hot. Show the order you would use to check the system out, by numbering from 1 to 3, the statements below.
..........Remove and check the thermostat
..........Check raw water discharge for flow
..........Stop and cool the engine and check the coolant level

5.         The engine lube oil pressure drops. Show the order you would use to check the system out, by numbering from 1 to 4, the statements below.
.......     Engine bearings
.......     Oil pump relief valve
.......     Oil filter
.......     Oil level

6. If an outboard engine fails to start. Explain how you might identify ignition or fuel problems by removing and checking spark plug.
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MAINTENANCE ANSWERS TWO

1. How can you quickly find out if a starting problem is being caused by a flat battery?
Try turning on work lights or other high power use equipment to see if they work. If the battery is flat, they will be dim or not on at all.

2.         The engine cranks but won’t start. Show the order you would use to check the system out, by numbering from 1 to 4, the statements below
4          Remove and replace starting aids
2          Check filters
1 Check fuel level and fuel cock
3          Undo the fuel line at the fuel pump outlet and check the flow

3. The diesel engine starts, but runs poorly and produces black smoke from the exhaust. What is the most likely cause of the problem?
Injection system problems.

4.         The engine starts running hot. Show the order you would use to check the system out, by numbering from 1 to 3, the statements below.
3          Remove and check the thermostat
1          Check raw water discharge for flow
2          Stop and cool the engine and check the coolant level

5.         The engine lube oil pressure drops. Show the order you would use to check the system out, by numbering from 1 to 4, the statements below.
4          Engine bearings
3          Oil pump relief valve
2          Oil filter
1          Oil level

6. If an outboard engine fails to start. Explain how you might identify ignition or fuel problems by removing and checking spark plug.
Inspect the spark plug gap. If the plug is clean and dry, there may be fuel supply problems. If it is wet and oily, the engine may be flooded.
If the plug is filled with carbon deposits, replace it.
With the plug wire attached and the plug body contacting the engine block, spin the engine over. A satisfactory spark should leap the plug gap if the ignition system is OK.

MAINTENANCE QUESTIONS THREE

1. Complete the statement:

“A four-stroke engine cycle takes ……complete turn/s of the crankshaft, while a cycle for

a two-stroke engine takes ............... complete turn/s of the crankshaft.”

2. Outline the main differences between the principle of operation of diesel and petrol engines.

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3. State the condition of the valves/ports and the position of the piston during:

(a) Induction in a diesel four-stroke

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(b) Compression in a diesel two-stroke

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(d) Power in a petrol four-stroke
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4 Explain how the cylinder of a two-stroke petrol engine is charged with fresh fuel/air mixture during induction.

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5. What checks and maintenance needs to be carried out to keep a heat-exchanger cooling system in good working condition.

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6. List the faults which could cause low oil pressure in a force feed engine lubrication system.

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7. List the faults which could cause fuel starvation in a diesel fuel system
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8. Before starting a vessel engine each day, state the things you should check.

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9. While operating a marine engine, state the things you should periodically check.

After starting the engine:

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After leaving the wharf, regularly check:

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10. List possible symptoms that could warn you that there is an engine problem?

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MAINTENANCE ANSWERS THREE

1.         A four-stroke engine cycle takes    two    complete turns of the crankshaft, while a cycle for a two-stroke engine takes    one   complete turn of the crankshaft.
2.         Outline the main difference between the principle of operation of diesel and petrol engines
Diesel engines inject fuel into the hot air at the end of the compression cycle, to ignite the fuel/air mix for the power stroke. Petrol engines use a spark plug and ignition system to ignite the fuel.
3.         State the condition of the valves/ports and the position of the piston during:
(a)        Induction in a diesel four-stroke
The exhaust valve is shut and the inlet valve is open. The piston is moving down the cylinder from tdc to bdc.
(b)        Compression in a diesel two-stroke
The exhaust valve is shut and the inlet ports are covered by the piston. The piston is rising up in the cylinder toward tdc
(c)        Exhaust in a diesel two-stroke
As the piston moves down toward bdc, the exhaust valve opens releasing combustion gases. The inlet ports are then uncovered by the piston at the bottom of the cylinder, and air is forced into the cylinder by the blower to push the burnt gases into the exhaust.
(d)        Power in a petrol four-stroke
With inlet and exhaust valves both closed, and the piston at the top of the cylinder on the compression stroke. The ignition system causes an electrical spark to jump the spark plug gap to ignite the compressed fuel/air mix.
4.         Explain how the cylinder of a two-stroke petrol engine is charged with fresh fuel/air mixture during induction.
As the piston rises on the compression stroke, the inlet port is opened into the crankcase, and the rising piston sucks fuel/air mix into the crankcase. When the piston goes down on the power stroke, the piston closes the inlet port and the descending piston compresses the fuel/air in the crankcase. As the piston approaches the bottom, the exhaust port is opened, then the transfer port is opened. The compressed fuel/air rushes into the cylinder through the transfer port.
5.         What checks and maintenance needs to be carried out to keep a heat-exchanger cooling system in good working condition.
Coolant level OK
Raw water intake weed trap, strainer, cock and heat exchanger clean
Pump bearings, seals, and impellers OK
Thermostat OK
All pipes and connections undamaged and not leaking.

6.         List the faults which could cause low oil pressure in a force feed engine lubrication system.
Low oil level
Relief valve stuck open
Blocked filter
Faulty engine bearings and components
Leaking pumps, pipes, or connections.
7.         List the faults which could cause fuel starvation in a diesel fuel system
Low fuel level
Fuel cock off
Blocked strainers and filters
Faulty fuel lift pump
Leaking pipes and connections
Faulty injector pump.
8.         Before starting a vessel engine each day, state the things you should check.

Visually check the engine, propulsion equipment, and bilge for:
            fuel, oil, water, or coolant leaks
            crushed or damaged hoses and pipes
            loose, broken, or damaged parts
These checks are usually done with engine and engine-room            cleaning duties

Check that the selected tank fuel cock is on

Check that the battery master switch is on

If necessary, check sea-water suction cock, strainers and weed traps

Check and drain sludge filter, if appropriate

Check the level and appearance of:
- coolant

lubricating oil of engine and propulsion equipment

The appearance of coolant and lubricating oil may warn you of problems oil scum in the coolant, or water sludge in the lubricating oil or fuel, can all mean trouble.

9. While operating a marine engine, state the things you should periodically check.

After starting the engine:

Check engine oil pressure. Make sure it is normal.

Check engine water temperature. Make sure it is normal.

Check lubricating oil temperatures (where appropriate).

Make sure they are normal.

Make sure the generator/alternator is charging.

Make sure alarms are switched on.

After leaving the wharf, regularly check:

Check engine water temperature. Make sure it is normal

Check engine oil temperature. Make sure it is normal

Make sure the generator/alternator is charging.

Check the engine for fuel or water leaks, and loose or damaged parts.

Check that the stern gland is not heating or leaking too much

Check the raw water discharge or tell-tale for water flow if necessary

Check for the sound of the engine and propulsion equipment. Rough running, excessive vibration, and unusual mechanical noises may indicate problems, and must be investigated.

Check for even, steady power from the engine, with no surging, hesitation, or flatness.

Check the exhaust:
- Black smoke or puffs from diesel exhaust indicate faulty injector/s or general problems with injection equipment.
- Black smoke from petrol engines indicate the engine

is running rich (too much petrol used).
- Blue smoke with lube oil shows faulty piston rings.
- White smoke from a diesel shows poor compression, but some smoke will often show before the engine

warms up.
- unusual exhaust ‘beats’ may also need investigation.
10. List possible symptoms that could warn you that there is an engine problem?

Engine won’t crank over.

Engine cranks but fails to start

Engine runs, but misfires or delivers reduced power

Blue, black, or white smoke present in the exhaust

Unusual noises from the engine

Lubrication or cooling system problems