MOTORHEADmotion to the boat that kicks
the transom to the side. Thus,
when trying to go astern, the
uninitiated skipper can sud-
denly find the boat going in
circles. Even shifting into re-
verse to slow down may cause
the boat to go sideways enough
that all it takes is an errant gust
of wind to put the boat at the
mercy of the elements.
We’ve written extensively
about prop torque in the past,
and you can learn more about
the phenomenon by visiting
boatingmag.com/how-to/how-
to-use-prop-torque.
Contra-rotating props, like
those of Project Disruption,
eliminate the kick caused by
prop torque. Since each prop
spins in a diferent direction,
each negates the sideways
by numerous sterndrive and
outboard oferings. Addition-
ally, ZF maintains that while
Project Disruption is initially
sized for tow-sports boats,
the concept could be scaled to
larger propulsion packages or
hybrid systems for a multitudethrust created by the other.
Contra-rotating propellers
have been in use since torpe-
does fitted with them in World
War II ran straighter than their
single-prop counterparts, and
they were popularized in the
recreational marine arenaof vessel applications.
I’ll be visiting the ZF Marine
headquarters in Italy later this
spring to meet with engineer-
ing staf. Following that trip
and (hopefully) a sea trial of
Project Disruption, I’ll file a
follow-up report.Project Disruption
features contra-
rotation: two props
on one shaft rotating
in opposite directions.PHOTO: COURTESY ZF MARINE