If you like to work on your own boat---install new equipment or troubleshoot and fix
problems that may involve a faulty pump or static on your VHF or a device that
sometimes trips an electrical circuit when you flip it on---or so your project doesn't wind up looking like this rats nest---you’ve probably
read Ed Sherman’s advice. Ed is the go-to tech guy at the American Boat &
Yacht Council (his formal title is vice president/education) who has literally
written the book on a lot of this stuff for marine technicians. He’s currently
teaching electrical courses for both ABYC and techs at the National Marine
Electronics Association. In his spare time, he writes a blog tailored for
boaters---it’s called Ed’s Boat Tips---and a column for Marine Electronics
Journal. Below is part 1 of a recent MEJ article that’s good reading for anyone
about to dive into some boat wiring.
By Ed Sherman
Selecting properly sized and rated wiring is something that
both the ABYC and NMEA talk about in all their training programs. But even with
that I’m still amazed at how many times we encounter undersized wire or wire
with totally inappropriate insulation properties being used onboard.
Tinned or untinned?
To get things rolling here let’s clear up one of the biggest
misnomers I run into at least annually. That is, does ABYC require the use of
tinned wire? The answer is that we do not and never have. Every now and then
I’ll run into a survey report that will state that the wiring on boat X does
not comply with an ABYC requirement for using tinned wire. This is simply
Now, is tinned wire a better choice onboard? The answer is
probably yes, but unlike others I would argue that it’s not as critical as
actually installing wiring in such a way that the tinning is essentially
unnecessary. The tinning’s sole purpose is to help mitigate corrosion. My contention
is that if wiring is installed so that water—one of the needed ingredients to
generate corrosion in the first place—is removed from the equation by building
into the wiring job things like proper drip loops, elevation of all wiring in
bilge areas to above the bilge high water mark, and in the case of sailboats in
both the static floating as well as the dynamic floating position, corrosion
should never be an issue.
Anyone with any experience onboard boats has seen the impact
on wiring from the occasional hosing down with sea water. As you cut off the
terminal and begin stripping back insulation you see the black colored copper
strands that are indicative of corrosion that has occurred due to water
migrating along the conductor via capillary action and leaving behind a ring
that is going to underperform. Tinned copper will help to slow down this
process for sure, but it will not stop corrosion from occurring altogether.
The best way is to install the wiring so that it will never get
water soaked in the first place. I’ve worked on plenty of 50 to 60-year-old
boats built before tinned wire was even available in our market. The wiring was
in excellent condition if it had been kept dry. So, tinned wire is nice, but
not nearly as necessary as some would have you believe.
What about the insulation?
Everyone will undoubtedly agree that the marine environment
can be harsh at times. Installations often require large tight bundles of wire
and cabling to get pulled through some pretty cramped areas on the boat where
heat can build up. For that reason, ABYC standards exist that talk about
derating of wire and cable depending upon how many current-carrying conductors
are bundled. The larger the bundle, the more the wires get de-rated for
Whether the cable is routed through engine room spaces where
average ambient temperature is going to be higher than outside the engine room
is one of the key judgement criteria found within the ABYC E-11 standard. Also,
understand that the actual temperature rating of the insulation material is
also considered here. The standard clearly states that nothing with a
temperature rating less than 75°C or 167°F be used in engine room spaces. Most of the “boat cable” in use today is rated
at 105°C, so this is rarely and issue. The only instance I can recall where I
saw this violated was with a battery charger that had a factory-installed flex
cord plug assembly with a 60°C rating on the cable. This was a new model
charger and the manufacturer replaced it without question.
Insulation properties must go far beyond temperature ratings
in marine applications. I can recall some years ago listening to a salesman at
one of the boat shows touting the fact that the silicon-based insulation on the
South African-built catamaran I was onboard was rated to 125°C. Quite
impressive except for one small detail that I didn’t discover until some years
later when I found myself doing some wiring work on a similar boat. The silicon
insulation, although quite soft and supple feeling, had extremely low chafe
resistance compared to any of the PVC insulation I had ever dealt with. In
fact, I discovered that I didn’t even need wire stripers to remove the
insulation as I could tear it off the wire with a pair of pliers with virtually
While teaching in South Africa about 10 years ago I
mentioned this interesting nuance to the group I was with, one of whom ran the
chandlery that provided the wire to the builders at the time. He was shocked,
of course, and explained that they wanted to keep business local and the
product was made in South Africa. Sorry, this stuff may have had more than
ample temperature handling characteristics, but more questions need to be
answered to determine suitability. How about chemical resistance properties, resistant
to oil and gas? Chafe resistance? UV resistance? Insulation voltage rating?
These properties need to be considered. In fact, the ABYC requirement is that
the pertinent information be embossed on the insulation jacket. Minimally, the
following specifications must be on the insulation jacket:
CONDUCTORS – DC & AC
Minimum surface marking of the individual conductors and
jackets shall include:
126.96.36.199.1.3 wire size, and
188.8.131.52.1.4 temperature rating, dry.
So, if you see a bunch of wire with no markings on the
insulation jacket, ask questions!
Next week: Sizing wire correctly.