Boating and Sailing.pdf - Moja ladja

Right Hand or Left?
Chapter 3: Picking a Proper Prop
When the engine is in forward gear, single-engine props usually rotate clockwise, viewed
from astern. This is called right-hand rotation. On dual-engine installations, it’s standard
procedure for the left or port engine to rotate counterclockwise, and thus it must be
equipped with a counterclockwise-rotating prop. This is called left-hand rotation. A righthand
prop won’t work on a left-hand rotating engine, and vice versa, unless the gearbox is
designed for continuous full-power operation in either direction.
Left-hand
rotation
Right-hand
rotation
43
Four-blade props offer more
lift for a quick hole shot and
run smoother than threeblade
props. However, they’re
more expensive and a bit
slower on top end.
(Photo credit: Stiletto Props)
On dual-engine installations,
it’s common for the engines
to rotate their props in opposite
directions to counteract
torque and make for easy
steering.
The idea is that when you’re going straight ahead, the opposite rotation of the blades
helps to steady the boat and causes it to steer straight easily. If both blades rotated in the
same direction, the back end of the boat would want to “walk” in that direction, forcing
the bow in the opposite direction. (For more on how prop torque or rotating force affect
handling, see Chapter 6, “The Art and Science of Docking.”)