Practical Boat Owner — November 2017

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PAINT AND

ANTIFOULING

Richard Jerram is

former UK technical

manager of

International Paint

GAS FITTING

Peter Spreadborough,

of Southampton

Calor Gas Centre,

has 20 years in the

industry

TRAILER-

SAILING

Colin Haines is a

design engineer

who has trailer-

sailed for 25 years

ELECTRONICS

Chris Ellery of

Greenham-Regis

Electronics is a

former Merchant

Navy officer

TOILETS AND

PLUMBING

Karl Sutcliffe of Lee

Sanitation knows

about holding tanks,

toilets and plumbing

YACHT DESIGN

Andrew Blyth is a

naval architect with

interest in stability

and buoyancy

WOOD

Richard Hare is a

wood technologist

and long-time

wooden-boat owner

50 of the most frequently asked boating questions are answered by our experts on the PBO website. Visit http://www.pbo.co.uk

BOATBUILDING

Tony Davies has

been building and

repairing wooden,

GRP and steel boats

for 40 years

e is running like a dog

Carburettor

cleaner may

only partially

solve fuel jet

blockages

Using the tender

can be the

trickiest part of

going boating

Edgar Liepens has a Yanmar

2GM20 engine like this – but

it’s running rough

SEA SAFETY

Top tips for safe use of a tender

This is the only

way to clean a

carb properly

• strip it and
  clean all the
  orifi ces manually.
  I suspect that what is
  happening in your case is that
  the jets have been coated in
  hard salts and that soluble
  deposits are also being
  deposited at the same time.
  The carb cleaner is cleaning
  the soluble deposits but not
  cleaning all the crud out. You
  then have a situation where
  the engine sort of runs OK till
  the build-up gets too much...
  and the cycle continues.

When I say it runs ‘relatively

smoothly’ I mean there’s a

constant vibration, but

generally acceptable for a

two-cylinder motor.

The problem manifests

itself as a series of soft jolts

from inside the engine or

gearbox, running at as little

as 1,000rpm under load. It

sounds like a ‘wuff wuff’,

approximately once per

second. Each ‘wuff’ is

supplemented by an

additional ‘impact’ that can

be felt all over the boat.

Increase the revs and is

becomes more intense.

Edgar Liepins, Latvia

STU DAVIES REPLIES:

It sounds as if there’s an

intermittent misfi re on one of

the cylinders. The ‘wuff’

puzzles me – but could be

explained by a sticking valve.

The ‘impact’ felt is likely to

be the cylinder that is fi ring

taking the load as the

governor tries to compensate

for the loss of power as the

other one misfi res. So we

need to fi nd out if one of the

cylinders is misfi ring.

First get all the tools

needed to slacken off the

injector nuts, along with

some thick pieces of cloth to

absorb diesel.

When the noises start, get

into a good position and

slacken off the injector nuts in

turn. Be careful: diesel from

the pump is under huge

pressure of around 3000psi

and can penetrate the skin –

which is why you need cloth

around the injectors to

absorb the diesel.

As you ‘crack’ the injector

nut one of two things will

happen. If the engine sounds

like it it’s going to stop then

you know that’s the cylinder

that’s working OK. If it makes

no difference then you know

it’s the bad cylinder.

Now you can focus on the

cause. Is it a sticking valve? Is

it a bad injector?

I’d take off the rocker box

fi rst and check all is good in

there. Look for excessive

clearances on the bad

cylinder’s valves or signs of

damage. If possible do this

after shut down when it’s

been running badly.

If all looks good then pull

the injectors and get them

checked, take note of the one

off the bad cylinder and pay

particular attention to that.

Q

What are your top fi ve

basic safety rules that

should be followed when

using a tender?

Kim Harman, Alvor, Portugal

KEITH COLWELL REPLIES:

This is a good question since

using a tender can be the

most dangerous part of going

afl oat.

■ Only use the tender when

the conditions are suitable. If

it’s too rough, or too windy,

don’t go.

■ Always wear a lifejacket.

■ Do not overload the tender

• better to make several trips
  lightly loaded – and make sure
  the weight is evenly
  distributed. If the tender is
  small, always step into the
  middle when boarding.
  ■ Carry a means of
  communication in case you
  need to call for help –
  handheld VHF, PLB or

personal pyrotechnics.

■ Carry an alternative means

of propulsion. For example,

paddles or oars if you’re

relying on a small outboard, or

emergency oars or paddles

if you’re under oars alone.

And if I were permitted to

make a couple more

additions, it would be to carry

a small anchor and warp

(depending on the depth of

where you’re boating), a bailer

or bilge pump and, at night, a

white lantern or torch.

ASK THE EXPERTS