If you really want to understand these rules, get a copy of "Farwell's
Rules of the Nautical Road". It has chapters on each rule, and
discusses all the court cases and how they've interpreted each. As far
as a "proper look-out" probably all of us violate that rule every time
we go out. Here's why:

Pg. 141 - Note 45. "The Supreme Court long ago established that the
lookout
must be exclusively employed in the lookout duties. (Supreme Court
Case
cited here).
Note 46. (court case cited here)..."a proper lookout must be someone
other
than the deck officer or helmsman"... (another court case cited)...
"required lookout can have no other duties that detract from the
keeping of
a proper lookout:.

That being said, there appears
to be a move underway to revisit the "one man bridge organization" or
OMBO.

Another comment out of Farwell's:
__________________
The term look-out implies watching and listening so that there is
awareness
of what is happening around the vessel. The emphasis is on performing
the
action, not on the person.

Senate Report 96-979 which accompanies Rule 5, permits the helmsman to
serve
as lookout:

On vessels where there is an unobstructed all-round view provided at
the
steering station, as on certain pleasure craft, fishing boats, and
towing
vessels, or where there is no impairment of night vision or other
impediment
to keeping a proper lookout, the watch officer or helmsman may safely
serve
as the lookout. However, it is expected that this practice will only
be
followed after the situation has been carefully assessed on each
occasion,
and it has been clearly established that it is prudent to do so. Full
account shall be taken of all relevant factors, including but not
limited to
the state of the weather, conditions of visibility, traffic density,
and
proximity of navigational hazards. It is not the intent of these rules
to
require additional personnel forward, if none is required to enhance
safety.

S. Rep. No. 979, 96 th Cong., 2d Sess. 7-8 (1980).
___________________________________________

The OMBO is still highly contested, and the courts still much prefer
a
dedicated lookout. Of course all this is moot unless you have a
collision
and end up in court, in which case the first thing they're going to
look at
is if you and the other boat had "proper look-outs".