Regal 3300 Owner's Manual page 144

CHAPTER 5
It may be necessary to switch "starboard" for "port" and vice versa.
In the following instance, engage both gear shifts in reverse with both
throttles in idle as backing begins.
As the boat begins to back, it will track in a port direction. By moving
in a forward direction with the port engine the boat will be forced to
turn and align with the dock. When you reach a comfortable alignment,
the port engine is put in reverse which will allow continued backing
to the dock.
Some adjustment in tracking can be realized by putting either control
momentarily in neutral or forward. Going forward on the port engine
pushes the stern to port; the starboard engine going forward pushes
the stern to starboard. Again, keep your calm and do not overreact to
the situation.
Twin Powered Boats Maneuvering
Twin powered vessel propellers are counter-rotating which will balance
steering torque. On most twin powered vessels the port propeller is
left-handed and the starboard propeller is right-handed. Mark the
propellers in case they ever to be changed or repaired at some point as
they could be mismatched on reinstallation since they both fit the shaft.
Moving forward with the starboard engine for a port turn, the propeller
offset from the centerline enhances significantly to pushing the stern
to starboard.
In reverse, the starboard propeller throws its thrust energy toward the
starboard side of the hull to assist in turning the stern to port. The
port propeller reversing, throws its thrust against the port hull side to
assist the pivot of the stern to starboard.
The important ingredients in turning and steering are combined by
the outward turning propellers. The steering result is used in the
same direction as the turning movement caused by the off centerline
propeller location.
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