Practical Boat Owner — November 2017

Here’s just a selection of the latest questions from

PBO readers. Email or write to the address on

page 5 and our experts will answer your queries

ENGINES

Got a question? Email [email protected]

Ask the experts

THE PBO EXPERTS To ask a question email [email protected] and include your address. Pictures are helpful

CRuiSing

Stuart Carruthers

is the RYA Cruising

Manager and has

sailed extensively

SailS

Ian Brown of the

International

OneSails loft group

is an expert on sails

ElECTRiCS

Paul Holland is

part-chair of the

BMEEA and MD of

Energy Solutions

(UK)

maSTS & RigS

Mike Coates worked

in the spar and

rigging business for

many years

EnginES

Stu Davies has

a background in

engineering in the

coal and oil field

industries

SuRvEy and

CORROSiOn

Colin Brown runs

a marine survey and

consultancy company,

CB Marine Services

SEa SafETy

Keith Colwell is

author of the

RYA Sea Survival

Handbook

SEaling and

BOnding

Gareth Ross is

Sika UK’s Marine

Market Field

Specialist

Q

I own a 2.5hp 4-stroke
Mercury outboard that
drives my Laser Stratos
keelboat when the wind
dies, and because there’s
rarely little wind the engine
doesn’t get used much.
Annoyingly, when I do
need it the engine has a
habit of failing, and always
for the same reason: issues
of fuel starvation.
The 2009 engine looks like
new. I keep it clean, flush
with clean water, and empty
the fuel tank and run the
engine dry if I have used it

• in fact its only burned one
  gallon of fuel since new! On
  top of that it’s regularly
  serviced by a Mercury agent.
  My engineer tells me my
  problem is a common issue
  because of the additives
  now in petrol, which will rot
  fuel lines and coat the
  carburettor with a brown
  vanish-like substance that
  blocks fuel jets.
  I’m told that by running the
  engine once a week you can
  reduce the chances of it
  blocking as quickly – but it
  will still block eventually.
  I’ve spoken to many other
  owners of small engines and
  they’re all experiencing the
  same issue – though people
  with older 2-stroke engines
  don’t seem to suffer the fuel
  blockage problem so badly.
  The agent’s cure is to soak
  the carburettor in a

commercial solvent – not

something that’s practical

when you are at sea.

Given that hundreds

(perhaps thousands) of PBO

readers own small 2.5-10hp

outboards has anyone come

up with an answer?

It’s not only a hassle to

keep taking the motor to an

outboard repair agent but a

safety issue as the motor is

my back-up. Although I carry

a radio, anchor and paddle

it’s still a risk if the wind dies

on a rocky coastline.

John Shears, By email

STU DAVIES REPLIES: A bit

of background first. Two-

strokes are effectively banned

for leisure use in the UK on

environmental grounds –

they’re considered too

smokey. So the big

Fuel issues for small outboards

My engine i

Q

The Yanmar 2GM20

engine in my boat

has had an intermittent

problem since I got the

boat four years ago.

It can be running

relatively smoothly for

many hours of motoring

at sea or manoeuvring in

port until, when re-

starting the engine, the

problem begins. This

problem may continue for

an undetermined period

of time and then, after

some sailing and for no

apparent reason, go away

again... until the next time.

manufacturers were forced

down the route of 4-strokes

which are easier to tune for

lower emissions.

Unfortunately one of the side

effects is that they have to

‘lean’ the mixture right down

at tick over and that’s where

the problem starts. They fit

tiny pilot jets and hide or do

away with the tickover idle

mixture adjustment to stop us

richening the mixture.

Modern fuels have up to 5%

alcohol/biofuel added and this

is highly reactive to some of

the plastics and rubbers used

in our carbs.

Also alcohol absorbs water

from the atmosphere, so we

have a perfect medium for

creating havoc with the tiny

pilot jets.

I’ve stripped down a lot of

these due to issues you talk

about. Inevitably there’s a jelly-

like substance in the float

bowl, but more importantly the

jets are blocked or coated with

a non-soluble metallic salt.

There’s a theory gaining

ground that the alcohol

additive is absorbing water

from the atmosphere which is

reacting with the brass jet

screwed in to the alloy body of

the carb. Electrolysis comes in

to play, which then produces a

hard metallic salt.

Carb cleaner was developed

for dissolving ‘varnish’ left by

evaporated petrol, but I’ve

found is that it doesn’t

dissolve the hard salts

deposited in the jets. Only one

thing gets rid of that, a hard

object pushed through the jet.

Since being an apprentice

50 years ago we were taught

never to push steel wire

through jets, that it would

widen the orifice causing all

sorts of problems!

In actual fact people like me

found out from practical

experience that pulling a wire

out of a wire brush gives the

perfect implement to gently

push through the jets and

clean the hard deposits out.

It rarely does any damage.

Even well-maintained small

outboards can fall foul of fuel

problems