Additionally, it is imperative that the elec-
tronics specialist involved with any installation
carefully check the interface protocols between
the autopilot computer and the GPS receiver
to ensure that all the necessary data will be
transmitted and received.Autopilot Installation
Most autopilots will function in a 10 V to
16 V range without incident. The 3% maxi-
mum voltage drop guideline applies here as
well, so be careful to consider circuit length
when calculating power feed wiring require-
ments. Autopilots are fairly heavy power con-
sumers, drawing anywhere from about 4 amps
to as much as 10 or 12 amps, depending on
the system. This high current draw is due to
the hydraulic pump/motor combination,
which is constantly working when the system
is on, and motors by their very nature are
heavy electrical consumers.
Note: Many of the manufacturer-supplied
electric motor drives are notrated for ignition
protection. These drives should notbe installed
in engine room spaces or fuel tank storage areas
on gasoline-fueled boats. Both the U.S. Coast
Guard (in CFR Title 33, Part 183, Subchapter I)
and ABYC Standard E-11 require that all
installations in these areas be rated as ignition
protected. Keep in mind that the CFR stan-
dards are mandatory; the ABYC standards are
considered voluntary.
Unfortunately, I see this requirement over-
looked on many boats, and it represents a seriousfire hazard if a fuel leak ever develops on those
boats. Check with the equipment manufacturer
that the motor drive is ignition protected if you
plan to install it belowdeck on a gasoline-fueled
boat. If it isn’t ignition protected, you should
swap it out for one that is.
Because autopilots rely on electric motors,
proper rating and placement of overcurrent
protection for the circuit and/or motor are
important considerations for the marine elec-
trician. In fact, this is true for any electrical
equipment installed on board, and the best
course is usually to follow the manufacturer’s
recommendations to the letter.
Finally, for the mechanic, it’s important that
whatever the steering actuation device is—
motor-driven lever action or hydraulic pump—
it must be securely mounted to the boat’s struc-
ture. Think through-bolts, not self-tapping
screws!
While it’s best to leave the final testing and
calibration of autopilots in the hands of the
electronics specialist, you can provide the same
basic quality control functions as with other
equipment:- Make sure the system computer is mounted
as far as possible from any RFI or EMI
emitters. - Check for interference by running the boat
under autopilot and, one by one, operating
all other electrical equipment. Obviously,
this test should be done in open water in
case interference does occur that causes the
boat to suddenly change course.
164 marine electronics installation and troubleshooting