the Yacht Thruster, requires drilling a one- to
two-inch hole (depending on the size of the
unit chosen) to attach it via a threaded pipe,
which is also used to route cabling. Another
external option is the Sideshift bow thruster,
which mounts to a vessel’s stem and uses no
holes below the waterline in its installation. In
fact, the manufacturer states it can be installed
while the boat is in the water. These units, while
simpler to install, are also exposed, making
them more vulnerable to impact damage.
SINGLE OR DUAL PROPELLER?
Another consideration when selecting a bow
thruster is whether to go with a single-prop
unit or a dual, counter-rotating-prop version.
Single-prop units cost less than compara-
bly sized dual-prop versions; however, the
dual-prop units are more efficient. Counter-
rotating props produce roughly 40 percent
more thrust than a single-prop unit while
using the same amount of horsepower. With
single-prop units, a lot of energy is lost in the
swirling motion of the water. Counter-rotating
units, where the second prop is spinning in
the opposite direction, are able to recapture
and refocus the energy of this swirling water
to increase their maximum thrust. Another
plus for dual-prop units is that smaller props
and tubes can be used to produce the same
amount of thrust, compared to a single-prop
unit. Smaller tubes, as discussed earlier, mean
better positioning and control.
BETTER CONTROL = MORE FUN
The ability to competently and confidently
maneuver a vessel (particularly a single screw
vessel) in challenging conditions is an art
form, one that doesn’t come in a flash of
inspiration. It takes practice. To many, myself
included, nothing beats the satisfaction of
melding the effects of wind, current, and the
knowledge of your vessel’s handling characteristics into a successful docking maneuver
under challenging circumstances. That said,
a bow thruster is simply another tool – one
of many that boat owners use while on the
Imtra/Side Power www.imtra.com
Yacht Thruster www.yachtthruster.com
water in their best efforts to get from point A
to point B as safely and with as little stress as
possible. I don’t view their use as some sort
of crutch to my boathandling skills. They’re
like a can of bear pepper spray. If you’ve ever
really needed one – and had it to use it –
you’re a convert for life.
Frank Lanier is a marine surveyor and holds a
100 GT master’s license. He has captained and
maintained many different types of vessels.
A dual-prop, externally mounted
unit with remote helm controls.