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Propulsion 2010

Rumors of the latest iPod are a hit on the street, but it’s the latest innovation in marine propulsion systems that are the real talk of the town. Read on and find out for yourself if pod drives really live up to the hype.


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With pod drives and forward facing duo-props, the latest technology in propulsion systems may appear unfamiliar but the benefits far outweigh the oddities. Photo: Seavee

Pod drives are far from a new concept in the marine industry. Cruise ships, tugboats, and commercial freighters have been utilizing these unique propulsion systems for decades. However, the beneficial aspects of these powerful thrusters have recently garnished impressive reviews within the recreational sector. With positive attributes including greatly improved fuel economy, unparalleled maneuverability, long service life, increased acceleration, and precise one-hand docking abilities, it’s no surprise revolutionary pod drives are the most widely talked about innovation among discriminating boat owners and technology-oriented boat manufacturers. Combining the hole shot performance of an outboard and the longevity of a diesel inboard, these progressive powerhouses offer open-minded boat buyers the best of both worlds…and so much more!

With a user-friendly joystick, average boaters can easily become experts at docking – even when faced with challenging conditions.

Before you decide to step into the pod drive market you need to ask yourself if these powerful propulsion systems are a solid fit for your particular application and desired needs. First things first, due to engineering and displacement, inboard motors are typically best suited for vessels exceeding 35-feet in length. While pod drives aren’t for everyone, there’s a reason boat builders are creating new molds and introducing new models to take full advantage of their benefits.

Volvo Penta IPS (Inboard Propulsion System)
Since its introduction in 2005, Volvo Penta has delivered over 10,000 IPS units to the recreational sector, giving the well-respected brand a commanding lead in market share over their closest competitor. As the first manufacturer to integrate this unique alternative to traditional inboard shafts, Volvo Penta has revolutionized the inboard market with options available to suit a wide range of high-performance vessels. Incorporating a completely integrated system from joystick and throttles all the way to twin counter-rotating, forward facing props, IPS drives offer boaters a wide range of performance enhancing attributes. With such great success and positive feedback on their initial line of IPS drives, Volvo Penta recently introduced an IPS system for their 11-liter workhorse, which means larger sportfishers can now utilize pod drive’s great advantages. The benefits of IPS drives are well known and as a result they’ve been adopted by many of the worlds finest boat builders. Currently, IPS drives are being utilized on more than 250 models from respected boat builders around the globe.

Perhaps the most appealing aspects of vessels equipped with IPS drives are their car-like characteristics with extraordinary maneuverability and improved fuel economy. With a user-friendly joystick, average boaters can easily become experts at docking – even when faced with challenging conditions. The joystick controls work up to 2,000 RPM with three selection points enabling the operator to determine the power level that’s needed depending on prevailing weather and sea state. While viewed as unconventional at first, Volvo designed their system with forward facing propellers mounted on the front of the drive unit. This enables the twin counter-rotating props to work in undisturbed water, which greatly increases efficiency as they pull a vessel forward.

With the forward facing design, most skeptics argue that the layout leaves the props susceptible to damage from floating or submerged debris. While it seems that this may be the case, Volvo has put plenty of thought into this concern. No matter what propulsion system your vessel employs, striking an object will no doubt cause a few headaches. When a typical inboard with a prop shaft strikes an object in the water, the prop, shaft and rudder will potentially experience serious damage. This kind of detrimental action often requires expensive and difficult repairs and most likely some serious fiberglass work. Volvo’s IPS drives were designed with pre-set separation points. In the event of blunt trauma, the drive shears off at the steering rack coupling, which leaves the hull sealed and eliminates the possibility of water intrusion. According to Volvo the required repair is relatively simple and fairly inexpensive.

For short-handed crews, Volvo’s Dynamic Positioning feature integrates a GPS anchoring system that utilizes satellite positioning to keep your vessel stationary, even in stiff winds and swift currents. Think about this; you’re headed out to go grouper digging and scout some new structures. Rather than repeatedly deploying your anchor and possibly damaging the important ecosystem, simply hit the Dynamic Position button and the onboard computer will automatically hold your position. Another facet that is sure to turn heads is the underwater exhaust discharge that’s built into the pods base unit. Choking on diesel fumes as you punch the throttles is a thing of the past with IPS drives.

When looking at Volvo’s product designations you need to understand their rating system. An IPS 400 does not mean 400 horsepower, but the horsepower required of a conventional inboard to achieve similar performance. As for routine maintenance, IPS drives have minimal service requirements. Since there is no need for shaft alignment and every part of the drive that is exposed to saltwater is manufactured of bronze or stainless steel, routine maintenance is limited to anode, oil and filter swaps.

In the end, Volvo offers an innovative propulsion system that greatly improves fuel efficiency and weight distribution, while simultaneously increasing deck space and reducing engine noise and vibration – all while providing state-of-the-art user-friendly docking and anchoring features.

ZF Zeus, in conjunction with CMD (Cummins MerCruiser Diesel), is the second player in the recreational pod drive market, although Caterpillar has recently partnered with ZF Zeus to utilize CATs legendary power systems. Both the Caterpillar and CMD powered Zeus pod feature counter rotating propellers, however, Zeus drives face aft like traditional inboard applications. While the maneuverability and docking abilities of vessels outfitted with Zeus drives rival IPS systems, one benefit of the Zeus system is the incorporation of integrated trim tabs. These automated trim tabs are located on the pod drive and make for precise adjustments during varying sea conditions. The trim tabs are linked to the boat’s onboard CPU and are optimized for each particular vessels installation. Manufacturers pre-set the tabs’ position, however, they can also be operated manually like conventional designs.

Zeus drives are designed to be installed in tunnels, whereas IPS drives are designed to mount directly to the hull. Because of the placement in the tunnel, only the skeg of the Zeus drive is exposed. Since all of the elements to the Zeus pod are situated in the tunnel, striking a submerged object will result in less damage to the props.

Like the IPS System, Zeus drives have the ability to turn independently, providing amazing high-performance handling characteristics. The onboard computer compensates for a vessels speed when turning and moves each unit accordingly. Zeus drives also offer a feature similar to Volvo’s Dynamic Position. ZF calls it Skyhook and with a built-in GPS sensor, electronic compass and inertia measurement unit, Skyhook can keep your vessel positioned in stiff winds and strong currents – basically working as an invisible anchor. To keep maintenance costs at a minimum, Zeus pods allow for all routine maintenance fluid changes to be done with the boat in the water. This eliminates the need for a costly haul out when regular maintenance is required.

When it comes to tackling big game, both IPS and Zeus drives feature characteristics that greatly improve a vessels ability to back down on trophy fish. Traditional shaft-driven inboards have a tendency to “dig” when backing down. With pod drives the thrust is directed parallel to the bottom of the hull, which keeps the stern from digging. Since these drives operate parallel to the waters surface they provide perfect horizontal thrust, compared to traditional inboards that feature drive shafts with downward angles.

There’s no denying the fact that revolutionary drives are here to stay. Improved efficiency is only one reason for this fact. With highly regarded builders like Viking, Spencer, Rampage, Calyber, SeaVee and Cabo utilizing pod drives, expect to see new designs improve in leaps and bounds from vanguard engineers who choose to utilize these revolutionary propulsion systems. The bottom line is that both Zeus and IPS drives provide superior efficiency and improved features in virtually all areas when compared to traditional diesel inboards. Both systems, however, are highly reliant on electrical systems and will set you back more than traditional drive systems. Do your homework and be sure to talk to the boat builders who utilize these systems. No matter which manufacturer you select, you’ll no doubt be impressed with the future of marine propulsion.