Boating New Zealand - May 2018

88 Boating New Zealand

engines and removing them), with a specialist engineering

irm TIG-welding a patch over the holes. he second, and

most important, step was to implement a sturdy bonding

strap between the engines and the aluminium hull. A piece of

70-amp, 10mm thick cable with two plated lugs ensures a good

connection that won’t easily degrade. his was bolted to the

engines on one end and to a crossmember on the aluminium

section of the hull on the other.

he third step was to coat the bottom of the sumps in a layer

of ibreglass, something Ovlov recommends. Trembath wryly

observed that many boat owners, especially those who repower

with secondhand engines, try to save money by not doing this

before installation. he irst time they have a leaking sump they

tend to rapidly re-think this approach. his process provides a

much more secure insulation layer than just a coat of paint, and

not only prevents the electrolysis problem, but also reduces rust

and other corrosion on the hard-to-reach sump.

Once we had the sumps back from the engineers we

stripped of the remaining paint, used a wire brush to lightly

scour the surfaces so the epoxy would adhere properly, and

created a completely waterproof ibreglass shell over the

outsides. Once this was dry, we then painted them the same

Volvo green as the rest of the motor and re-itted the pans to

the engine blocks.

he inal mitigation was to reduce the maximum level of

water that can ever be present in the bilge. Older boats with

worn seals and bearings will always get some water ingress,

and unless we were absolutely diligent about cleaning this

every time we went out it would likely recur. However, the

depth of water present could be reduced by implementing an

alternative sensing switch.

Some market research uncovered the Water Witch

electronic bilge control, available from Marine Express

in Rotorua. Rather than relying on a loating mechanical

element, this unit has no moving parts and detects the

presence of water across a pair of contacts. he manufacturers

claim it works even if the water is contaminated with oil or

dirt, and it triggers as soon as there is about 2cm of water.

In addition to

a a permanent

solution, there

are also options to help reduce corrosion which are simple to

apply. One such product is Salt-Away, which acts as a corrosion

inhibitor and can dramatically reduce the damage caused by

water sitting in the bilge for a period of time. It is efective even

in salt water, lasting up to 12 months at a ratio of at least 500:1,

and in fresh water will last indefinitely.

Because bilge pumps always leave a bit of water in the bilge,

adding a small amount of Salt-Away means you get lasting

protection for a small investment. First work out how much water

your bilge holds when the pump has got rid of the excess. In our

case this was just over 10 litres. At 500:1 this worked out to 20ml

of Salt-Away. However, this is the minimum ratio after pumping

out excess water, so we added 50ml of the product. The light

blue colour of the resulting water is a visual indication, and once

this fades we will add some more Salt-Away.

SALT-AWAY

CORROSION

INHIBITOR

his implies the bilge pump may kick in more often than with

a mechanical loat switch, but it ensures the net water level

remains much lower. he Water Witch has a manufacturer’s

seven-year warranty and comes in both 12v and 24v versions.

In the end we elected not to replace the existing bilge pump

and loat switch, but rather to install a second unit with the

Water Witch controller. By positioning this at the opposite end

of the bilge to the existing pump (and, coincidentally, closer to the

TANGAROA ARARAU

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Gain the skills for your Maritime NZ licence

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The Engine Room Ltd

Sole NZ Agents for:
BETA MARINE

PH: 09 480 2248 FAX: 09 480 2258

34 Enterprise St, Birkenhead, Auckland.

E-MAIL: [email protected]

If re-powering ask about our unique

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