Power Supply
The scene is classic. The boatowner boards his
boat and fires up the radar, color chartplotter,
fishfinder, VHF, and whatever other electron-
ics are on board, reveling in the glory of all of
that expensive techno-wizardry. Life is good.
Then he starts the engines... only to see all
the electronic equipment blink out.
What’s happened here is simple: engine
cranking draws a lot of amperage, and in this
case it pulled the system voltage below the min-
imum operating parameters set by the electronic
equipment vendors. Fortunately, no permanent
harm has been done. Once the engines are run-
ning (and assuming the engine alternators are
functioning normally), voltage will stabilize, andthe equipment will come back online and func-
tion normally. But that momentary loss of
power can cause any microprocessor-controlled
memory function within a given device to
“dump” the memory, which is a major hassle if
the unit in question has a lot of data entered.
This scenario is not only inconvenient, it’s also
one of the most common electrical/electronic
problems experienced on boats, and it drives
some owners crazy.
You can adopt one of three strategies to
address this problem:1 The NMEA recommends installing a sep-
arate, isolated battery bank to supply all
the electronic equipment. This bank can
be fed by the engine’s alternator for136 marine electronics installation and troubleshooting
You can use a miniature “pot fan” to supply forced-air circulation behind enclosed electronics
panelboard arrangements. Coupled with some additional louvers to let fresh air into the
space, small fans can help tip the temperature scale in the right direction. A word of caution,
though; these fans are not typically rated for ignition protection, and therefore they should not
be used in places such as battery boxes or gasoline engine rooms where ignition protection is
mandatory.