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What do civil and military aircraft; military vehicles, electric
fork lifts; busses, motor coaches, commercial craft and
many of the US Navy’s and Coast Guard’s small vessels have
in common? Most utilize 24-volt electrical systems and, in
the not too distant future, Detroit and foreign passenger car
manufacturers will begin producing automobiles that utilize
24 or 36-volt electrical systems.
Although a small number of boat builders have embraced
the 24-volt concept since electrical systems first found their
way aboard recreational vessels early in the last century, of
late they have been rare in boats under 60-feet. Recently,
however, 24-volt electrical systems have gained popularity
in more vessels and in smaller vessels, and with good rea-
With each boat show I attend, I notice that the number of
vessels equipped with 24-volt electrical systems grows. The
addition of a greater number of, “high demand” DC loads,
electric bow thrusters (nearly all of the more powerful elec-
tric units are only available for 24 volt service), inverters,
windlasses, sheet winches, davits etc. have played a signifi-
cant role in the resurgence of the 24-volt marine electrical
system. These high ampere devices call for larger and larger
DC cabling, cabling that becomes particularly cumbersome,
heavy, difficult to install and expensive when operated on 12
volts. The reasons for this 12/24-volt disparity will be dis-
cussed in detail in a moment.
Why has it taken so long for boat builders to rediscover this
more efficient medium for electrical conductivity throughout
the vessels they build? The answer is simple; most DC gear
found aboard boats has, or had until 10 or 20 years ago, its
roots in the automotive industry which, since the 1950’s has
been almost exclusively a 12 volt club (prior to that, most
cars and trucks used
6-volt electrical sys-
tems). Manufacturing
electrical equipment
in relatively small
numbers, exclusively
for the marine mar-
ket, is particularly
cost ineffective. Thus,
manufacturers of ma-
rine electrical gear,
everything from cabin
and navigation lights
to pumps, fans and
blowers, borrowed as
much as possible
from standard auto-
motive and industrial
12 volt materials and
equipment. Accord-
ingly, as the country
further industrialized
and Detroit’s impact
on that industry grew,
it became more and
more efficient to standardize marine electrical systems a
12 volts. Good for the manufacturer’s and the consumer’
pocketbook (and good for the folks who owned stock in c
per mines and cable manufacturing, again you’ll see why
a moment), but bad for the efficiency of the marine elect
cal system. The reason for switching from 6 to 12 volts in
the 1950s is the same reason for switching from 12 to 2
By Steve D’Antonio
24-Volt Commercial Equipment
24-Volt Bow Thruster
Heavy DC Wiring