"Low Transoms - The single most critical reason boats are flooded on open
water has to do with transom
height. Most boats that are swamped are outboard powered, with engine
cut-outs that are often only
inches above the waves. Motor wells are supposed to be the second line of
defense when a wave comes
over an outboard's transom but, in some cases, the well is too low, too
shallow, and/ or not sealed
adequately to the cockpit. Scuppers in the motor well and cockpit may also
be slow to drain, especially if
they re clogged. And whenever water lingers in the well or cockpit, the
chances of another wave coming
aboard increases. So too is the risk of being swamped."


"A boat is often much "closer" to the water than its freeboard would
indicate. A cracked
thru-hull at the boot stripe or a cutout at the transom for an outboard
motor well that isn't
protected by a splash guard means that, as a practical matter, the boat has
to sink only
an inch or two before it floods and heads to the bottom. Inspect fittings
and hoses above
the waterline with the same critical eye that you used on fittings down in
the bilge. Double-
clamp the thru-hulls and consider adding an anti-siphon loop or check valve
to any that
are within 8" to 12" of the waterline"


http://www.boatus.org/onlinecourse/R...s/section3.pdf