Last year, I wrote about Volvo Penta's revolutionary new IPS drive system that couples diesel engines to lower units mounted on the bottom of a boat's hull instead of on the transom. In service for some time now, IPS is finding its way into the sport-fishing fleet, most notably aboard a 43-foot Spencer express boat, which many people test drove at the Fort Lauderdale Boat Show last October.
This new drive system offered substantially increased efficiency, enabling builders to achieve desired speeds with smaller diesel engines. It also increased maneuverability by allowing you to aim the entire thrust from the propellers in almost any direction. Since the introduction of IPS, Volvo Penta enjoyed having the market for this innovative drive system all to itself.
But that's about to change. Cummins MerCruiser Diesel has been working on a similar drive system of its own, named Project Zeus. CMD introduced the concept at last year's Miami Boat Show, giving a glimpse of what the system would offer. Like IPS, Zeus consists of diesel engines matched to drive pods positioned on the bottom of the boat, just forward of the transom. But Zeus differs from IPS in quite a few areas.
For instance, the props on Volvo's IPS drives face forward like the propellers on most airplanes, pulling the boat through the water. Like IPS, Zeus drives use two counter-rotating propellers on each drive pod, but the Zeus props face backward, pushing the boat like most conventional drive systems do. And Zeus drives mount in hull tunnels, whereas the IPS drives mount directly on the hull of the boat.
"With the Zeus drives, only the skeg is exposed," says Rob Mirman, CMD's manager of strategic planning and the program manager for Project Zeus. "Everything else is in the tunnel, so if you hit an obstruction, only the skeg should break off."
Mirman and CMD have been working with the boat brands within the Brunswick boat group to design these tunnels into the boats, but they also work with non-Brunswick brands. "We have developed mold inserts to accommodate the various boatbuilders we're working with," says Mirman. "They don't have to change their molds; they simply add the inserts to the boats being built for Zeus drives to create the tunnels."
Extensive testing on Zeus-equipped boats reported impressive results in terms of efficiency and speed. For example, on a pair of identical 45-footers, one equipped with Zeus drives coupled to 425 hp diesels and the other with twin 500 hp straight inboards, the CMD engineers gained 4 mph in cruise speed with the smaller engines and 2 mph at top speed. And the ability to gain speed with smaller engines, which obviously burn less fuel, translated into a whopping 30 percent increase in efficiency at cruise, a truly impressive number.
This increase in efficiency comes from several factors. First, the hydro-dynamic drive pods greatly reduce drag when compared to all of the hardware associated with conventional inboards. Second, the propellers on the Zeus drives operate parallel to the water's surface, providing perfectly horizontal thrust for maximum efficiency, unlike inboard props, which all come with an inherent down angle that bleeds power.
Cummins makes the Zeus drives out of heavy-duty bronze and stainless-steel components to ensure years of reliable service. This power configuration also reduces vibration substantially, and all exhaust exits underneath the water so it will surface far behind the boat.
But Zeus drives offer lots more than just efficiency. A host of innovative features built into the system makes these drives truly revolutionary. The drive pods turn independently of one another in their respective tunnels, providing unparalleled high-speed handling characteristics and low-speed maneuvering capabilities. "The drives rotate a maximum of 15 degrees inward and 45 degrees outward," says Mirman. "The system's computer takes factors like the boat's speed into account during a turn and rotates each drive unit accordingly." So if you're executing a high-speed turn to port, for example, the port drive pod, which is rotating outward (toward the chine) will turn more than the starboard drive, which is rotating inward (toward the keel).
The ability to steer the drives independently brings other benefits as well, most notably a feature called the Skyhook Electronic Anchor. "Every Zeus drive comes with a built-in GPS sensor, an electronic compass and an inertia-measurement unit," says Mirman. "When you press the 'Skyhook' button and activate that feature, the GPS captures the boat's position, and the CPU then keeps the boat centered within a very tight radius of the initial setting."
Think about that - you pull up to your favorite deep-drop spot, you press the Skyhook button, and the computer automatically adjusts throttle and drive angle to counter any effects from wind and tide that seek to move the boat off of your spot. Just press one button, and the boat stays exactly where you want it, automatically.
Along similar lines, the joystick that comes with the Zeus drives allows you to dock with unprecedented ease. "Captains will stop using the throttle levers to dock once they see how easy the joystick system works," says Mirman. "It provides complete vessel control at a single point."
The joystick works as a combination of a trolling valve and steering control. You simply push the joystick in the direction you want the boat to move, and it goes there. When the joystick is moved slightly off center, the transmission slips, and the props turn very slowly. The farther you move the joystick from the center, the more the transmission engages, and the faster the props turn. If you rotate the joystick knob, the boat will spin around in place solely with the thrust from the drives - no bow or stern thrusters are needed.
Zeus drives also come with integrated trim tabs built in. "The tabs work automatically and are linked to the boat's speed," says Mirman. "The operation of the tabs is optimized for each particular boat." That means when the boat is accelerating and climbing out of the hole, the computer might angle the tabs down to provide a little extra lift and then retract the tabs automatically as the boat settles into a level running attitude. The factory will pre-set the automatic positions as the boat is built, but you can also operate the tabs manually like conventional trim tabs, or you can offset one tab or the other while operating in the automatic mode.
Mirman also points out that the Zeus drives provide enhanced reliability through the use of redundant systems. "We use multiple wires to control the system," he explains, "so that even if one wire gets damaged, there's another one to make sure the system will still function." Zeus also comes with digital throttle and shift, for smooth and precise control, and with all of the monitoring capabilities of Mercury's SmartCraft system.
Zeus drives come in two model designations, the 3500 and the 3800, and will be coupled to Cummins diesels up to 550 hp. You can mount the engines directly to the drives or connect via a jackshaft. It's not clear exactly when the new Zeus system will hit the market, but it's coming soon. When it arrives, consumers will benefit from yet another power option that brings a high level of efficiency, maneuverability and innovation to the offshore
For more information, visit www.cmdmarine.com/projectzeus.html.