| GAS YOURSELF, Explode Yourself - or not ! The vast majority of twin engine gasoline powered boats and a very high percentage of single engine boats (sailboats included) I survey have improperly and unsafely ventilated engine campartments. Why you should be concerned ….. Two reasons ….. 1.) Carbon monoxide is poison. 2.) Gasoline fumes can explode. There is no bigger safety leap you can make that is so easy and so cheap to do right. This is so simple and so inexpensive to do right that I find it hard to believe so many boat builders still get it wrong. I am not talking about older boats here. Check out the new models in the showroom and you'll be hard pressed to find one done right. Is your family worth $20.00 worth of flexible duct work from your local hardware store ? While this issue is critical on gasoline fueled boats, CO from diesel is just as deadly as CO from gasoline. Diesel does produce less CO than gasoline but you must remember that CO poisoning is cumulative and will build up over hours or days and may take up to two weeks to leave your bloodstream. For more on CO take a look at Carbon Monoxide Poisoning. What makes this particularly insidious is that CO poisoning closely mimics the symptoms of seasickness. |
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| The following recommendations are based on ABYC® " Ventilation of Boats Using Gasoline" Standard H-2, with a little common sense thrown in. The diagram at right shows a properly ventilated boat with A, B & C being exhaust outlets with blower fans and with D and E being fresh air intake ducts. 1. All three powered exhaust ducts draw air from under their respective engines. Gasoline vapours are heavier than air and will seek the lowest level. The space directly below the engines may not be the very lowest level but are generally bordered by tall stringers which contain the fumes to these areas. The whole excercise here is aimed at drawing possibly gasolineand/or CO fume laden air from these areas and directing it overboard. 2. ABYC® requires one blower for "each gasoline engine used for propulsion". I think they screwed up here and forgot about the generator. Did they think generators couldn't leak gas ? I always include genny blowers in my recommendations. Once again, stringers or other structural frame members can trap heavier than air vapours so it's essential that each area have its own blower. 3. All powered exhaust ducts should exit on the same side of the boat with fresh air intakes on the opposite side. Neither intakes nor outputs should be on the stern of boats with accomodation spaces. If intakes and outputs are on the same side you may end up re-circulating the same gasoline vapours. I also often see intakes and output connected to the same plenum which is a surefire way of re-circulating vapours rather than ventilating your engine compartment. With intakes and outputs at the stern, The "station wagon effect" may push fumes back in through the intakes. |
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| Some believe that it is not necessary to
run the blowers at cruising speed and
turn
them off as soon as they are under
way. I
prefer to see blowers run whenever
the engines
or generator are running but they most
definetly
should be run when the vessel is moving
at
slow speeds and at anchor if the generator
is running. |
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| A few other ABYC® requirements…. Exhaust ducts must terminate
in the lower 1/3 of the bilge but above
the
normal accumulation of bilge water.
Exhaust
duct ends must be no closer than 24"
to intake openings. Air intakes and
exhaust
outlets shall be no closer than 15"
from gasoline fill and tank vent fittings.
Ventilation outlets
must remain outside of weather enclosures.
You will get better cross ventilation
if
the intake ducts are high in the engine
compartment.
All duct ends must be secured. ABYC and NMMA also prohibit ventilation intakes
or outputs at the stern (on boats with
accomodation
spaces) due to the "station wagon
effect"
and the fact that people tend to hang
around
the swim platform with the generator
running. Of course none of this makes any difference if you don't use your blowers. Canadian law requires that blowers be run for a minimum of 4 minutes before starting your engines. Keep an eye out this season and watch most people flick the blower switch and immediately fire up their engines. The insurance investigation takes place shortly thereafter. Think I'm exaggerating ? take a look ................. |
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| One of many at the Toronto Boat Show and
is an affront to all boat buyers. Note
all
the intake and output holes across
the stern
(round holes below the seat back) and
right
under the "NMMA Certified"
sign,
a clear violation of common sense,
ABYC and
NMMA standards which the manufacturer
claims
to meet. Then they have the temerity
to put
a CO warning label (shown below) on
the transom
! ..............  ..................CO can cause brain damage ! Maybe this builder .....................spent too much time on his own boats. |
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| At right - Another Regal with intake &
output transom ventilation (those three
slots
just above the name) within inches
of each
other but they are not alone. Below right - Or this one This one vents into the cockpit ! Below - Just to prove I don't have it in for Regal, here is a Maxum with the same setup. The builders are well aware of ABYC® Standards and NMMA (National Marine Manufacturers Association) is their own organization. Why can't they get it right? Why don't you call and ask them before you hand over your deposit cheque ? |
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| Turn on this blower and the duct end just gets sucked tighter to the deck and provides no exhaust from the engine compartment at all. Intake and output duct ends must be secured in a manner that permits free flow of the air. | These intake and output ducts terminate within inches of each other and are connected to the same plenum at the other end. This ain't rocket science. No way is this engine compartment being ventilated it's just sending the same air round in circles. |
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| This blower draws air from under the transmission but any gasoline fumes will collect forward of the drip pan bulkhead under the engine will remian untouched. | For about $4.00, a length of duct could be added to this blower leading under the engine (on the other side of the stringer). |
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| At right - Air intake butted agains outboard
side of stringer, Air intake on wrong
side
of stringer and both lead to the same
plenum.
With CO poisoning and seasickness having
virtually the same symptoms how do
you know
which one you are experiencing. If this is your boat I suggest you find out ! |
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| Shown below is one of my favourites. Close
up your canvas and block your fresh
air intakes
and blower ouputs (just above the transom
doors on both sides), Blower output
is forced
into a sealed cockpit. Waddayathinks gonna get him first, asphyxiation or explosion ? |
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| Sailboats are not immune. I have surveyed hundreds of gasoline powered sailboats and have never yet seen one properly ventilated (never seen one ignition protected either but that's another article). This fella put a vent from his engine compartment directly into his saloon. |  |
