Are Not Pressurized Like Cars
Why Do Boats Burp?
Grounding Essentials and a Special Warning
Why Are Boat's Fuel Tanks Inaccurate?
ARE NOT PRESSURIZED LIKE CARS!
Cars utilize a pressurized system to deliver fuel directly to engine
injectors. This is done under high pressure delivered by a pump
within the fuel tank to assure peak performance and economy. This
type of system also does not permit air or fuel to escape from the
tank during operation and does not have a vent to relieve pressure.
Cars also have a carbon canister to control vapor emissions.
According to the Boat
Safety Act of 1971, pressurized systems are not permissible for
boats. If they were, in the event of a failure anywhere in the system,
a large amount of fuel would collect in the bilge creating a very
explosive situation. In addition, boats pound more while underway
and fuel gets jostled, causing additional expansion. The pressure
created must be released – and on boats, it is released though
the tank’s breathing vent. Shake a can of soda and open the
top and you’ll know the explosive answer as to why boat fuel
systems aren’t allowed to be designed like cars.
DO BOATS BURP?
rapidly or overfilling your fuel tanks, boats vent air that is often
mixed with fuel. During refueling, gas goes into the tank and displaces
air. The air escapes out through your boat’s fuel tank vent.
When the tank is nearly full and there is no more air to displace,
frothy fuel begins to bubble out into the water or onto your decks.
of the fuel (and subsequent leaks out of your boat’s fuel
vent) may occur when cool fuel is pumped from underground storage
tanks into the boat on a hot day, or during the rise and fall of
For these reasons, you
should never top off your fuel tank and you should always leave
10% of tank capacity for expansion. Also try to refuel when you
are headed out, not when you are putting the boat away. Trailer
boaters should take the added precaution to fuel their boats on
a level surface, or air pockets can form in the tank that can lead
to the burping or back splash of fuel.
ESSENTIALS and a SPECIAL WARNING:
About Grounding Your Deck Fill: Please check with your installation
instructions regarding grounding requirements or refer to a marina
or boat yard that is versed in American Boat & Yacht Council
(ABYC) construction standards.
nozzles are metal and the flow of fuel through it generates static,
a small but dangerous spark (called an Electrostatic Discharge or
ESD) can occur when the nozzle is inserted into a metal filler neck.
To prevent sparking, a ground wire must be attached from the metal
deck fill unit to the boat’s bonding system. Also, it is
important that the nozzle remain in contact with the metal deck
fill at all times while refueling. Never wrap a nozzle in an absorbent
pad or rag so that it prevents a good contact between the nozzle
and metal body of the deck fill. When refueling portable fuel
tanks, always place directly on the ground, never on a plastic truck
bed-liner or a dock made of synthetic plastic wood. Good contact
between a portable tank and a solid grounded object is essential.
for Plastic Body and Metal Fuel Caps: Deck fill units that have
a plastic body with metal components such as a metallic lid or metal
retaining chain, are NOT to be grounded. Read the important Safely
Message & Technical Bulletin issued by the United States Coast
Guard (USCG) in February 2005:
Guard Warning: Fuel Fill Technical Bulletin:
events have caused the boating industry to examine the
policy regarding the bonding of plastic body fuel fills
with metallic caps and retaining chains. Existing USCG
& ABYC policy states that the bonding of these components
is voluntary. A study by IMANNA Laboratories has shown
that connecting the metallic retaining chain and cap
of a plastic body fuel fill assembly to a boats bonding
system may result in electrostatic discharge from a
land-based fuel pump nozzle to the metallic components
of the assembly when the boat is not in the water. This
condition does not exist when the boat is in the water
due to the equalizations of the ground potentials between
the fuel pump nozzle and the boats bonding system.
is recommended by ABYC and the USCG that new and existing
installations of this type of fuel fill assembly DO
NOT INCLUDE any attachment to the boats bonding system.
Existing connections should be removed from the point
of connection to the boats bonding system to the fuel
fill assembly. Removal of the metallic components of
the assembly is not necessary; however, the U.S. Coast
Guard and ABYC still require that METALLIC body fuel
fills be bonded.
further information contact:
John Adey, ABYC (410) 956-1050 ext. 29 firstname.lastname@example.org
Richard Blackman (202) 267-6810 email@example.com
ARE BOATS FUEL TANK GAUGES INACCURATE?
why so many boats have problems with fuel gauges so we asked around
about why gauges seem to be inherently inaccurate. The response
from manufacturers was “don’t blame the gauges!”
Rather, the most common culprit cited was the sending unit (that’s
why tapping on the glass rarely works)!
Most fuel gauges
rely on a sending unit with a float that is often manufactured by
a separate company. The float rises and falls with the fuel level
and sends an electronic signal corresponding to a unit of measurement
(usually ¼ tank increments) on your fuel gauge. Often, new
boats are shipped on trucks when the fuel tanks are empty, causing
the sender to bounce and become misaligned. Another potential reason
for inaccurate readings is that tanks are often designed to fit
the bottom contour of a boat and sometimes shaped like a triangle.
This means that the sender and gauge must be compatible with unique
tank shapes, and dropping in a stock sending unit is not likely
to read accurately.
In addition to issues
with the float arm and tank shape, there may be calibration, voltage
fluctuation or grounding issues at play. The bounce, heel, trim
and general abuse that a boat takes when operated affects proper
readout as well. Have you ever come off a plane and suddenly have
a different readout?
If your boat
has some fuel gauge issues: 1) Manually inspect the sending unit
in the fuel tank. Be certain it has no internal rubbing or an obstruction.
2) Check for proper voltage, wiring and ground connections and determine
if the sender and gauge are compatible. 3) Visually calibrate by
refilling your tank in known increments and make a few hash marks
with an indelible marker right on your in-dash gauge at these intervals.
This process will take some time, because you must return the nozzle
to the pump and properly ventilate your boat (at least 4 minutes)
each time before turning on the key to check the gauge to avoid
a potential explosion.
If you have questions, comments or would like to share some personal
experiences or observations, please contact
BoatU.S. Foundation for Boating Safety & Clean Water
147 Old Solomon’s Island Rd. Suite 513
Annapolis, MD 21401
Findings #40 Main Page