Marine Diesel Engines in Yachts. (How they work) Part 1

We have produced the first of two videos to help explain how Marine Diesels work. This was requested by a couple of our viewers. Hope you enjoy both parts.
NB. The intercooler is after turbo and the intake not before. To give cool air into the combustion chamber. We noticed the error in the voice over too late to change it.

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Closed Captions (CC):
how your engine works

some things you need to know in this

video

we're going to look at diesel boat

engines

we're going to look at how they work how

they need to function

we're going to look at fuel injection

and lots of other stuff

stick around you never know you might

learn something

[Applause]

[Music]

[Music]

we're going to start with the basics

first

know your engine now whether you've got

a volvo penta

a yamaha a nanny a betamarine

or even one of the lombardi series of

engines there's some stuff

some basics that you really need to know

the first thing you need to know is your

engine number

there may be a number of different

engines using the same block or the same

components

but they can differ you need to know

this number especially

if you're ordering parts individual

engines may differ but let's look at

some of the components

i'll use this volvo engine as an

illustration mainly because the parts

are easy to identify

like the alternator starter motor

the water pump or coolant pump

the raw water pump or salt water pump

the exhaust outlet which sometimes has

an injection elbow

and then on modern engines there's a

control box usually containing a few

relays and a fuse

few bits and pieces let's move on

you need to identify specific

maintenance points

like the header tank for the coolant the

dipstick

to check your oil the oil filler cap

your engine oil filter your diesel

filters

then there's your diesel pump and

finally

your injector pump

and your injectors now as i said

engines will differ but the same basic

components

you'll find on all diesel engines

okay let's look at some of the engine

parts

or engine components let's start at the

bottom

with the sump then there's the crank

the connecting rods pistons

the combustion chamber or cylinder

within the engine block

the valves and the valve seats and the

cylinder head which contains the valve

gear

and then the rocker box cover or cam

cover which keeps the oil in the engine

now your engine may have a turbo it may

even have

two the exhaust gases come out

at high speed from the exhaust manifold

and into the turbine

the turbine has a shaft that goes

through it and this shaft

turns another turbine at the other end

this turbine or compressor compresses

air

and forces it into the engine

because the air is compressed there's

more of it and the more air that goes

into the engine

the more fuel can be put in to give you

a bigger burn

more power some engines are exactly the

same

apart from the fact one has a turbo and

one doesn't

the one with the turbo gives out more

power

the main backbone of your engine is the

crankshaft

and you can see one here this is an

eight cylinder crankshaft

the crankshaft is connected to the big

end

of the connection rod the top end of the

connection rod the small end

is connected to the piston as the

pistons go up and down

this reciprocating motion is turned into

rotary motion

the crankshaft will be connected to a

camshaft

either an overhead cam or an overhead

valve type

and it's this cam that drives the

rockers which push the valves down and

allow the exhaust gasses

out and fresh air in

on an overhead cam engine the cam is

over the top of the engine

but it's still driven from the

crankshaft and still pushes the valves

down and opens and closes them at the

right moment

so that's how it works so whether you

have an overhead valve or overhead cam

engine

it's the cam that drives the valves now

the bit

all you school boys have been waiting

for suck squeeze

bang blow okay stop your giggling at the

back

depending on what type of engine you

have some will have a pre-heater

which is in the top of the cylinder head

and heats the air

as the piston comes up some will modify

the injection

in order to get the engine started and

warmed up

either way the principle is the same

okay on the

intake stroke or suck stroke or

induction stroke

the inlet valve opens and air is drawn

into the cylinder by the piston

dropping down the ball on the

compression or

squeeze stroke both the valves are

closed and as the piston comes up

the air inside the cylinder is

compressed

in a diesel engine this rate of

compression is extremely high

as the air is compressed it heats up

to about 550 degrees celsius at just

about the moment of maximum compression

or top dead center roughly diesel fuel

is injected as a spray

this pressure can be as much as 40 bar

or 600 psi

this spray mixes with the hot swirling

air and spontaneously

explodes bang we call this the power

stroke

the rapidly expanding gases force the

piston down

inside the cylinder as the crankshaft

rotates

the piston then goes back up and ejects

the hot gases and exhaust

out through the open exhaust valve hence

suck squeeze bang blow

or induction compression power

exhaust a four-stroke engine there are

some engines

which are diesel and two-stroke

these are mainly commercial engines made

by people like

detroit diesel obviously being a

two-stroke you get twice the power of a

similarly sized four-stroke engine

but perhaps we'll look at them another

time

diesel engines have some specific needs

in order for them to work efficiently

we've looked at diesel fuel systems

before previous videos

but suffice to say diesels need to have

very

clean fuel the injector pumps are

complicated

and can be subject to damage if they

have dirty fuel here's how it works

a diesel pump has a shaft which drives

cams

these cams push pistons up and down

and as the pistons go up and down the

liquid that cannot be compressed

is then ejected out through the

particular port

for whichever cylinder it's the timing

of this pump

to the crankshaft and the position of

the piston which is critical to having

the engine

firing at the right point

meanwhile at the injector the fuel

enters the injector

and goes down through a gallery where it

meets a nozzle valve

the predetermined pressure is reached

this valve

lifts and injects diesel into the

cylinder

or combustion chamber diesel injectors

and pumps work at extremely high

pressures

so be careful and to be honest if you

don't know how the pump works

you shouldn't really be playing with it

some of the fuel

left over from the injection is allowed

to travel back up the injector

and out from the leak off pipe this then

returns back to your tank

this surplus fuel helps to cool the

injector and also lubricate it

preventing wear as technology advances

we're now seeing more common rail

diesels used

as marine diesel engines the type of

pump on these diesels

has just one single outlet going to a

common rail

the injectors on this type of engine are

energized

by a solenoid being told to fire by the

engine's ecu

so it's an electronic allowing of the

pressure out the nozzle

but the principles the same this

computer control of the injection point

has distinct advantages in that the

injection point can be advanced

or as the engine speeds up or

slows down

however electronics and salt water don't

always mix well

number five what do diesels need

well diesels need to have a cool clean

air supply and that's why you need to

have a good quality air filter

and preferably some forced air

ventilation

this is particularly true for turbo

engines

and it's one of the reasons that most

turbo engines have an

intercooler the intercooler cools the

air going into the turbo

before it goes into the combustion

chamber the reason for this

is that cold air is denser than hot air

so again

a bigger bang diesels need to have a

good

quality oil as recommended by the

manufacturer

and it needs to be changed on a regular

basis

we've talked in previous videos about

how important the cooling system is

on marine diesels marine diesels create

heat on the compression stroke

as well as on the power stroke keeping

the engine at the right temperature

is fundamental to its operational

efficiency

because diesels compress air for the

power stroke

there needs to be good bores good piston

rings

and a good seal around the valves the

valve stem

oil seals also need to be in good

condition especially on the inlet

valve or oil can be drawn down the inlet

valve guide

and into the combustion chamber diesels

also need to have a clean

and clear exhaust especially around the

exhaust

injection elbow not having a clear

exhaust

causes excessive back pressure excessive

back pressure

will cause low performance from your

engine

and also can prevent all the exhaust

gases

escaping from the combustion chamber

okay let's look at smoke let's look at

black smoke first

black smoke is unburned or partially

burned fuel

the most common cause for this is

overloading which is sometimes referred

to as

over fuelling because more fuel is fed

into the engine that can efficiently

burn

the causes for this can be fouled prop a

blocked exhaust

elbow or even poor compression from a

badly worn engine

but it can also be from bad injectors

injectors are not clean

or not adjusted correctly or it can be

the injector timing

all of these need to be looked at okay

let's look at white smoke this can have

many reasons

it's often difficult to diagnose what

those reasons might be

however generally it's caused by low

compression

a failure of the compression stroke to

reach its full

temperature remember when the piston

comes up on the compression stroke

it's actually heating the air in order

to create the burn

so what the causes well generally

they're engine wear

rings balls valves valve guides and

seals

but don't mistake smoke for steam

remember that steam will dissipate

within a few feet of the boat

but smoke won't it will linger

okay let's look at blue smoke this is

normally accompanied

with excessive oil use poor performance

excessive crankcase pressure the causes

well generally it's engine wear to

things like valves

valve seats and seals piston rings and

bores

or low oil pressure all of these

point to you burning oil

okay let's look at not starting poor

starting

this can be a number of reasons but

here's some of them

you can have a warm starter or the

starter circuit might not be operating

correctly

it can even be a flat battery one of the

things that uh

fails quite often are the starter relays

or the pre-heat fit

relays for your heaters the heater is

not working either heaters themselves

have failed

you can have low compression by worn

wings

bores or valves blocked or reduced

exhaust ball

that can cause a lot of starting

problems the timing can be wrong

or it may need adjusting it does need to

be adjusted from time to time

now here's another top tip if your

engine doesn't start within a couple of

goes

do not keep cranking the raw water pump

will continue to push water into the

engine

and basically you'll fill your exhaust

pipe up

when the exhaust is full it will then

flow water

back into the engine and the engine will

go hydraulic

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[Music]

in the next video we're going to look at

pre-start

and fault finding so we'll look at the

checks you should do

and things you should look for we're

even going to put together a pre-start

list for you

which will soon be available from our

website until next time

thanks for watching and don't forget to

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