Four winns Vista 328 Owner's Manual page 28

J. Backdrafting (Station Wagon Effect)
Backdrafting or the “station wagon effect” is caused by
air movement over or around a boat creating a low pres-
sure area of suction area around the stern which can
increase CO level on the boat. Backdrafting can be af-
fected by relative wind direction , boat speed, and boat
trim angle. See Figure B9 Backdrafting - Airflows Over
Boat and Behind Transom”.
Under certain speed and operating conditions the low
pressure area may form in other regions and permit car-
bon monoxide to enter the hull through openings that
are not on the back of the vessel. Boat factors which
may affect CO concentration:
Figure B9: Backdrafting - Air flows over boat and
behind transom.
1. Inefficient trim angle. See Figure B10.
2. Excessive or unequally distributed weight.
Figure B10: Inefficient trim angles.
3. Canvas Configurations - Under various conditions,
adding or removing canvas may raise or lower CO
levels. See Figures B9, B10 & B12.
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Exhaust Fumes!
Hull exhaust from your boat can cause exces-
sive accumulation of poisonous carbon mon-
oxide gas within cockpit areas when using pro-
tective weather coverings (while underway or
while stationary). Provide adequate ventilation
when the canvas top, side curtains and/or back
(aft) curtains are in their closed protective po-
sitions. (See Preface for actual warning label
regarding carbon monoxide and weathering
cover/canvas.)
4. Opening and closing ports, hatches, doors, and win-
dows may raise or lower CO levels on board a boat.
See Figures B11 and B12.
Figure B11: Desired air flow through the boat.
Figure B12: The effect of canvas configurations.
K. Cabin Appliances
Boats having fuel burning appliances in accommodation
areas should be provided with adequate ventilation and
maintained to function properly.
L. Air Conditioning
It may be possible for carbon monoxide to be brought
into the air conditioned space by the air conditioner. If
installed, please refer to the air conditioner
manufacturer’s literature for additional information.
Section B
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