• The helm is a steering wheel or tiller with
its related gear.
Direction on a Boat
• Forward is the direction toward the bow
of the boat.
• Aft is toward the stern.
• Facing the bow, the right side of the boat
is starboard.
• The left side is port. (Figure 1-2)
Dimensions of a Boat
• Length overall (LOA) is the most common
term used to describe the size of a boat.
It is measured from the forward part of
the bow to the after part of the stern. It
does not include attachments that are not
part of the hull, although bow pulpits and
swim platforms become part of the overall
length of a boat.
• Waterline length is the measurement
along the waterline from the point
where the bow touches the water to the
point where the stern emerges from the
water.
• Beam is the maximum width of the boat.
• Draft is the depth of the boat underwater.
• Freeboard describes the distance from the
water’s surface to the lowest part of the
gunwale or transom.
• Bridge Clearance is the maximum height
of the vessel above water. (Figure 1-3)
Powerboat Terms
• Inboard power uses an engine mounted
internal to the boat with a shaft extending
through the hull to a fixed propeller
under the hull. The propeller is mounted
in front of a rudder.
• Outboard engines are self-contained units
that mount on the transom. A lower unit
is suspended in the water aft of the boat
and contains the propeller, which can be
Section 1: Getting Started 3
Aft
Starboard
turned to steer the boat. The engine can
be tipped to adjust the angle of the propeller
or to raise it from the water.
• Inboard/outboard (I/O) drives have lower
units resembling those of an outboard
engine. The lower unit connects through
the transom to an internal engine. The
boat is steered by turning the lower unit.
• Jet drives use an impeller mounted in a
tube to pull water in from under the hull
and propel it rearward to provide thrust.
The nozzle on the drive is turned to steer
the boat.
• Horsepower is a measure of the power
produced by the engine.
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Figure 1-2. Direction on a boat
Port
Forward
Figure 1-3. Dimensions of a boat