Hallo Miljenko,


You are right, there is no reason to put 24V instalation in boat smaller
than 60ft. All boats with higher voltage than 12V have **V/12V inverters
for
audio/video/instruments/??lights. El. current in 24V instalation is 1/2 of
12V instalation with same load so all wires can be thinner but voltage is
higher so insulators must be better and higer voltage instalation is much
more sensibile to electro-corrosion than 12V.

The electro-corrosion is dependet on the resistor or the cable and the
current so the effect is smaller
with lower current as is in 24V systems.
The isolation should not realy be a problem at 12 or 24 Volts.

The needed wire size is for a given device 1/4 of the 12Volt wire. The
reason is
that you need 1/2 of the current and you can accept the double amount of
voltage to be lost on
the way.
To make it clear i´ll try to give an example.
at 12 Volt you need 100 Watt. The wire has 0,1 Ohms for the plus wire and
0,1 Ohms for the return line
you see 10 Amps and lose 2 Volts at the wire. The 100 Watts are drawn from
10 Volts at the user.

At 24 Volts with 100 Watts you see 20 Volts at the user at 5 Amps the wire
could use 2 Volts each witch means
a resistance of 0,4 Ohms each so you need 1/4 of the copper.

The bigest loads on boat are motor starter (motor batery is usually close
to
motor so wires are short and there is no problem), bow-thruster and anch.
winch (use only 2 large wires to connect "+" and "-" of service battery
with
relays mounted close to thruster or anch. winch) command wires are not
problem.

Heavy Inverts for 120/240 Volts at 3000 Watts are very difficult to run on
12 Volt.

The reason for my boat to use 12 and 24 Volt systems was that i was not able
to
get a warm water heater around 24 to 30 KWatts at 12 Volts because this
things
are made for trucks and busses and so they are using 24Volt systems. The
heater
runs with fuel but has a high pressure pump and some electric inside.

Michael