STERN DRIVE MANEUVERING
Inboard/outboard, I/O or sometimes called stern drive boats do
not have rudders. e boat uses a steering system that directs the
propeller thrust, by turning the stern drive unit where the propeller
is mounted. Normally maneuvering the I/O boat is easier than a
similar single screw vessel.
Directing propeller energy (thrust) makes slower speed maneuvering
easier. e propeller discharge current is turned from one side to
the other which results in turning forces. Rudder boats need water
to ow by the rudder to be e cient. Stern drive units are designed
to have reduced sha angle, so the propeller does not produce as
much unequal blade thrust and resistance as does a propeller on a
single screw boat. Large horsepower stern drive boats do produce
more thrust and steering torque but your vessel has the advantage
of power steering. Below is some basic information on how single
stern drive boats handle in normal conditions.
Gathering Headway
When a stern drive is not moving forward or reverse in the water
and the propeller is not turning, (shi in neutral) the boat will not
react to the helm steering wheel.
As soon as the vessel is shi ed into forward gear the propellers action
creates a discharge motion and generates energy in the form of thrust.
If the stern drive is centered, the discharge motion is directed straight
back causing the vessel to advance forward.
You may notice that if you advance the throttle quickly in initial
take-o (make sure you have a rm grip on the wheel), the boat
has a tendency to pull the stern of the vessel to starboard. ere is
a trim tab (also serves as a sacri cial anode) located on the vertical
drive housing just to the top of the propeller blade. is trim tab
helps compensate for the low speed steering torque. Once the boat
increases headway and the propeller is operating in a faster water
ow this torque e ect decreases.
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