have previously established a baseline for
the circuit, as with cranking ampsNormal figures for older, noncomputer-
ized engines must provide a reading of over
9.6 V while cranking. Modern engines should
always read in excess of 10.5 V.Interpreting the Results
Voltage and amperage readings can tell you
many things beyond whether the starter cir-
cuit is in order. Particularly on modern boats,
which are increasingly powered by electronically
controlled engines, excessive system voltage
drop during engine cranking is a concern. For
example, assuming the connected battery has
tested OK, voltage readings that are lower
than desirable may indicate that the battery is
too small (i.e., not enough capacity) for the
task at hand, or that the wiring is too small for
the job and an upgrade is required.
Cranking amperage is also of concern, as
mentioned above, but historically, engine
manufacturers have been more than a little shy
about sharing relevant cranking amp specifica-
tions with technicians or end users of their
products. In the old days, 1 amp per cubic
inch of engine displacement was the rough
rule of thumb, but this applied only to gaso-
line engines. Diesel engines, with their much
higher compression ratios, often pulled far
more than 1 amp per cubic inch.
Starter motor technology has changed, too.
The 1 amp figure was reasonable for old-style
field-wound motors, which characteristically pull
more amperage. But with the evolution to perma-
nent magnet–type motors, gear reduction motors,
and such, starter current draws have decreased
dramatically in the last ten to fifteen years.
Therefore, as with other measurements,
starter current draw as a diagnostic tool is only
as good as the information you start with. Do
you know what the draw is supposed to be? If
you are working on the same systems repeatedly,28 electrical systems troubleshooting
or the starter in question is on your own boat,
establish a benchmark when everything is func-
tioning normally. Log this number and the tem-
perature at which the value was measured for
future reference. Remember, cold temperatures
will increase the load on the starter and cause the
motor to pull more amperage. Typical draws for
modern starter circuits range anywhere from
150 to 850 amps at 80°F (27°C). At 80°F, any
variation from the norm that exceeds about
±10% to 20% indicates a problem.
Higher than normal current draw could indi-
cate a seized engine, although this should have
been ruled out already. (Remember, you are prob-
ably performing these tests to establish the cause
for slow engine cranking. A partially seized engine
is generally the result of an extreme overheating
incident, in which case the temperature gauge
would have registered over 215°F (102°C). The
vessel’s history and other symptoms will usually
confirm or deny this possibility.) Assuming the
engine is in good condition, higher than normal
current draw is probably a problem internal to
the starter motor. Remove the starter for further
inspection and repair as needed.
Lower than normal current draw is a classic
symptom of loose or corroded cable connections
or undersized wiring (which will show on the
inTELLECT EXP-1000 as higher than normal
loop ohms resistance). You may need to conduct
additional testing to determine the location of
the excessive resistance within the circuit. If the
wiring checks out OK, then the problem is
within the motor itself.
Charging System Test
The third test under the System Test (main
menu) is the charging system test. As with the
other tests, it is easy to perform by following
the unit’s on-screen prompts. The cable con-
nections are the same as for the battery and
starter tests, with the possible addition of the
amp clamp. (If you are following the meter’s
system test procedure, advance to the charging