LETTERS TO THE EDITOR
DOCK VOLTAGE SAFETY
I always enjoy Steve D’Antonio’s
articles and admire his passion for
boating. So, I need advice regarding
dock voltage because no one else is
able to answer my questions. My
vintage Hatteras utilizes one power
cord ( 50 amps, 125/250 volts, 2
pole, 4 wire). I travel up and down
the West Coast including Mexico,
where voltage varies based on the
marina. Some marinas show 208
volts, others 215 volts, and still
others 225 volts.
What is considered low voltage
and harmful to pumps and motors? I
have a buck-boost transformer that
supplies a 10 percent increase.
When should it be utilized and is
low voltage better than high
voltage? What is considered high
and harmful? Which way should
you error if you have to?
Scott
San Diego, California
Your questions are very good,
indeed, Scott. In short, electrical
gear that is designed or specifically
wired to operate on 220/240 volts
should not be operated on 208. This
is particularly true of motor loads
such as refrigeration and HVAC
compressors and pumps like the ones
used to supply raw water to the
HVAC system. When supplied with
this low voltage and increased
amperage (ampere draw is inversely
proportional to voltage draw where
inductive/motor loads are concerned)
motors run slower and hotter,
drawing more amperes, which can
lead to their failure.
You can look at the commission
plate on this equipment to determine
its voltage requirements. Although
it may not be harmful, other gear
such as battery chargers, will have
diminished output when operating on
low voltage (many are designed to
operate on a wide range of voltages).
Additionally, if the vessel is receiving
208, or less because of voltage drops
resulting from the length of the
dock, the output of the 120-volt
system will be precisely half of 208,
i.e., 104 or less. Needless to say,
that’s highly undesirable.
I’ve never seen an example of
utility-supplied high voltage, however,
it could be created by an improperly
wired transformer. I’d be concerned if
you saw anything over 250 volts.
Always check your volt meters before
turning on any branch circuit
breakers to ensure that voltage isn’t
too low or too high.
Ideally, you should see voltage no
lower than about 220 and 110 volts
on these two systems. If it’s less,
the boosting transformer should be
doing its thing. Remember, there’s no
free lunch, a transformer of this sort
adds voltage by borrowing some
amperage, so the amperage available
to you when it’s doing this will be
something less than 50.—Steve
D'Antonio
ENGINE OIL QUANDARY
I have always enjoyed Steve
D’Antonio’s articles in PMM. In
fact, they are the first stories I read
each issue.
I believe that I have read in past
articles that he recommends oil
temperatures at around 135° to
140° when the engines are fully
operational. I have twin Perkins
240hp engines that run about 105°
to 115°, but I live and operate the
boat in Southeast Alaska, so that is
not too surprising. Could he please
explain the reason for the higher
temperature? Also, I believe that Steve
has suggested a diverter for the
cooling water to raise the temperature
to the desired level. Would you also
suggest where I might purchase
diverters for my engines?
Lee Thompson
Petersburg, Alaska
Thanks for your comments and
question, Lee. While it varies
somewhat from engine to engine,
oil temperature should be above 160°
and no higher than about 230°. If the
oil is operating at about the same
temperature as the coolant, i.e., 175°
to 195°, that’s ideal. Why is this
important? When the oil temperature is
too low, it allows the deposition of
sludge and varnish inside the engine,
on bearing surfaces, and inside oil
delivery galleries, and it makes it
more difficult for water (typically
from condensation) that has entered
the oil to evaporate. If the oil runs
consistently too hot, admittedly not a
problem for most displacement vessels,
then it suffers from shearing (loss of
viscosity) and thermal breakdown.
If you have an oil cooler it’s
probably not thermostatically
controlled (few marine diesel
engines have thermostatically
controlled oil coolers, some
Cummins Q series are among these).
Adding such a thermostat
is an option, however, I know of no off-the-shelf kits for doing so. Oil
thermostats are popular for industrial
applications, trucks, hot rods, and
other automobiles (I added one to my
1974 Triumph), so the parts for doing
this exist. Adapting them to your
engine while maintaining maximum
reliability would likely require the
service of an experienced and creative
mechanic. Even if you have an oil
cooler with a thermostat, there’s no
guarantee that the oil will reach ideal
temperature if the load is consistently
light, as is often the case.
An alternative would be to simply
operate the engine at 80 percent load
for 10–15 minutes for every four
hours of running time. Doing so will
almost certainly increase the
temperature of the oil to the ideal
range (measure the temperature
carefully at the middle of the oil
pan), which will keep at bay the
