Practical Boat Owner - July 2018

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

Andy Haines of

Greenham-Regis

Electronics is an

expert in marine

instrumentation

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

CORROSION

ELECTRONICS

Folding prop protection

GPS feed failure

Q

I have a Volvo Penta

D1-30, with Volvo

folding prop and a

ropecutter, all new last year.

On liftout, after nine

months afl oat, the saildrive

leg anode was only about

25% corroded, but the

three-part ring anode on the

prop had completely

corroded away, leaving only

the mounting screws.

There are very slight

traces of ‘pinking’

(dezincifi cation) near the

mounting screws, but no

actual corrosion visible.

My boat is in Mercury

Marina on the Hamble, and is

fi tted with a galvanic isolator,

although I believe the prop

is mounted on a rubber

bush, and therefore isolated

from everything else.

The local VP dealer tells me

that the prop anodes only

last about six months –

which seems unacceptable

to me. Is there anything I

can do to avoid replacing

Q

I have a Furuno GP32

GPS that feeds a

Simrad AIS, Raymarine

chartplotter, ICOM SSB and

VHF radios. I inherited it

with the boat, a 1990 Rustler

36 bought in October 2015

and currently in Rodney

Bay, St Lucia. I think the

GPS is 15-20 years old and

works fi ne, but the other

instruments are not

receiving the feed. I am not

aware of any specifi c event

on board that might have

triggered the feed failure.

Charles Griffi ths

Winchester

ANDY HAINES REPLIES:

Firstly, the Simrad AIS

(assuming it is a transceiver)

should have its own GPS

antenna. If it is a receive-only

unit, it doesn’t need a GPS

feed as such – the location is

being derived from within the

plotter. Therefore, the Furuno

GP32 is feeding NMEA0183 to

the plotter, the SSB and the

VHFs. While it is possible to

feed two or more devices from

one output, it’s also possible

the GP32 is slightly

overloaded – especially if

there is more than one VHF.

First thing to check is that

all unit interconnections are

intact and well made. Also,

just make sure that the NMEA

output is set correctly. Try

NMEA REM-1 or REM-2,

options found under Menu -->

I/O Set Up.

If the NMEA output has

failed it’s not cost effective to

repair because the price of

spares plus labour is more

than a replacement. Possible

replacements include the

Furuno GP39 or Garmin 158i:

both are excellent, neither

is expensive.

bolt holes to concentrate the

wasting on the thicker parts of

the anode. For more visit

https://bit.ly/2qOuA2Z.

I wouldn’t recommend

cutting another groove in the

propeller without consulting

the manufacturer. You may

weaken the hub and cause it

to break off: at very least

you’ll invalidate any warranty.

It might be possible to get a

bigger anode made but the

bolt holes will always be a

weak point.

It would be worth checking

whether there is any electrical

connection between the

propeller and the saildrive.

The propeller should be

electrically isolated from the

saildrive but the rope cutter

could act as a bridge to

reconnect them. If this is the

case then the propeller anode

may be protecting more metal

than it was designed for.

the anode mid-season?

In the photo you can just

about see the anode

mounting screws sitting in

the groove in the prop

bush... one at about 12

o’clock, and the other at 8. I

wonder whether it’s possible

to have a second groove

machined in the boss, and

then fi t a second anode?

Steve Hoskins

Havant, Hampshire

COLIN BROWN REPLIES:

This is a common problem

with Volvo folding propellers.

The anode is quite thin and

has three bolt holes where the

anode tends to snap off as it

wastes away, hastening its

demise. A contributor writing

on the YBW/PBO Reader to

Reader forum back in 2011

reported getting better life by

applying a spot of paint

immediately either side of the

Steve Hoskins’s

Volvo folding prop