by John Page Williams
photography by Michael Wootton
In the late 1950s, Mead Broaddus, the older brother of one of my school classmates, built a 20-foot cabin cruiser from a plywood kit. Being handy, progressive in his thinking and the proud owner of a 1958 Volkswagen beetle, he powered the boat with a standard 36-hp air-cooled VW engine. More to the point, the engine was turning an inboard-outboard drive that facedforward. Unfortunately, the engine did not have enough power to tow my friend on water skis, and the outdrive hit a snag and broke. Soon enough, the engine became a spare for the car, the outdrive went into a storage shed forever, and the plywood cruiser got a pair of outboards.
That outdrive's inventor had a good idea, though: Position the propeller ahead of the drive-like an airplane prop-so it pulls the boat by biting into undisturbed water. A good idea indeed, but it took 50 years to move it out of hobbyists garages and onto the drawing boards of mainstream boatbuilders and engineers. Meanwhile, with the advent of sophisticated deep-V hulls and lightweight diesel engines, sport yachts and large fishing boats have gotten faster and faster. But at speeds above 30 knots, efficiency declines quickly on boats using conventional inboard drive systems with angled-down propeller shafts. Some manufacturers have responded by molding propeller pockets into their hulls to reduce the drive angle, but the limitation is still there.
Then Volvo Penta stepped up to the plate. Last year, at the Miami International Boat Show, the company introduced to the public its Inboard Performance System (IPS). IPS mates a pair of Volvo's new-generation 310- or 370-hp D6 diesels with common-rail injection and electronic control to dual-propeller outdrives that face forward. In addition to the two above benefits, IPS also places the engines and drive units farther forward than on a conventional inboard-outboard system, resulting in improved hull balance. In fact, the drive units can be fitted with jackshafts to move the engines forward even more, giving boat designers more options for achieving good balance. Volvo Penta claims that the increased efficiency of the drives gives the 310-hp engines the same performance as 400-hp diesels with conventional drives, and the 370s the same as 500-hp engines. These two systems are designed specifically for performance cruisers and sportfishers 35 to 50 feet in length that cruise at 20 to 40 knots.
Do they work? To find out, we visited Jackson Marine Sales in Northeast, Md., where owner Woody Jackson and salesman Tom Ruggiero gave us the opportunity to put a Regal Commodore 3860 Sport Yacht with an IPS 400 through its paces. The short answer to the question is yes, absolutely. But along with the surprising hidden advantages to the system, there are also some drawbacks.
How IPS Works
The IPS drive unit looks like a heavy-duty, hydrodynamic conventional inboard/outboard with Volvo Penta's well known counter-rotating DuoProp setup, except that it faces forward, with a large opening at the rear to vent exhaust gases into the prop wash. Every part in contact with seawater is either a special nickel-aluminum-bronze alloy or stainless steel.
The circular mounting collar through the hull is just aft of the engine, with a rubber suspension system at the interface between the drive and the hull, which includes seal rings to keep the water where it's supposed to be. Installation requires a technician to raise the drive from under the boat. When it's connected to the D6, a universal joint takes the thrust from the drive shaft and sends it down to the planetary gear set in the drive to turn the propellers. Throttle, shift and steering are all electronic, with the hydraulic reverse gear and the steering system mounted on the top of the drive. Right now, Volvo offers the IPS only in dual installations. A Regal Commodore 3860 with conventional inboards has V-drives with the propeller shafts set in pockets under the hull. On the IPS version, the drive units mount on flat surfaces, perpendicular to the bottom and on either side of the 18-degree-deadrise OceanTrac hull.
What if these forward-facing IPS propellers snag a crab pot or run aground? Rick Pruitt, Director of Diesel Product Support for Volvo Penta, has logged several thousand hours aboard IPS-equipped boats, especially the company's 38-foot Tiara. He's found that for pot lines and modest-size wooden objects, the counter-rotating stainless steel propellers act like the "spurs" that many inboard boatowners install on their shafts to cut snagged lines. He cites running through a pot-infested channel in the Nansemond River near the boat's home port of Suffolk, Va., and cutting through a four-inch tree branch while running down the canal from the St. Lawrence River to Lake Champlain. Of course, he always tries to avoid such obstructions, but he's glad to know that the drives can generally take care of themselves when the unavoidable occurs-though not always.
A more serious incident happened last spring while Pruitt was running up the Gallant Channel of the Intracoastal Waterway between Beaufort and Morehead City, N.C. "I'm a main channel guy," Pruitt told me. He was traveling at 27 knots in the Tiara, with one Volvo colleague below and another beside him at the helm, monitoring the depthsounder and GPS, when suddenly they were on top of a sandbar that had shifted into the channel. The port drive hit bottom a hard but glancing blow. It forced the bow down into the sand, which stopped the boat abruptly. All three men were hurt, one seriously (all have recovered). The situation was not much different from similar ICW incidents in boats with conventional twin-engine inboard drives, but the IPS-equipped rig is supposed to shear off under such a direct impact, lessening the chance of injury to people on the boat and avoiding structural damage to the boat hull.
What went wrong? While Volvo Penta engineers designed the IPS drives to shear off under direct impact, this grounding was apparently not direct enough. It's worth noting, though, that there was never any prospect of the boat sinking. According to Pruitt, Volvo worked with the boat companies using the IPS to design the laminate schedule to withstand more than the shear force for the IPS struts. That way the IPS struts will snap before the hull fails. After the Gallant Channel grounding, Pruitt took a tow in, but the boat actually still ran, though slowly. The port shaft mount and clutches were damaged, and the props were bent. The cost of repairs was about $2,000, plus $1,500 for a new set of props.
An IPS-equipped boat also draws more water than one with conventional bare-shaft drives set in hull pockets. Our Regal test boat requires about four feet, compared with just over three for the same boat with pockets.
The advantages of the IPS system seem to far outweigh any inherent problems, and heading the list are improved performance and, surprisingly, simplicity. Pruitt points out that the cost of repairs in the ICW incident was low compared to the damage that a conventional inboard would have sustained, and very low compared to the V-drives often mounted in sport yachts like the Tiara 38 and the Regal 3860. With the IPS, there's no propeller shaft to align, no packing glands, struts, rudders, mufflers or raw water strainers to install and take care of. A short exhaust hose connects to a flange on the drive unit that runs to the vent underwater. Indeed, the dual IPS drives in the Regal's engine room make a compact, neat installation under the boat's cockpit, offering easy access to all service points. Pruitt also pointed out that setting up a warranty for an IPS-equipped boat is simple. "It's just us and the boat [manufacturer,]" he said.
As to performance, running the Regal Commodore 3860 was a real joy. The Northeast River and the channel on the east side of the Susquehanna Flats were calm on test day. In the slip, the exhaust from the D6s vented through bypasses to the hull sides, creating slight currents. Once under way, Tom Ruggiero demonstrated the IPS's maneuverability by easily making tight 90-degree turns to work out of the slip and around the marina's fairway.
Once in the river, the Regal rose onto plane easily, though depressing the 12-by-24-inch trim tabs helped keep bow rise to a minimal six degrees. By 2400 rpm and 16 knots, the wake was flat, with two plumes of foam from the drive units. The largest sea we could find was two feet, coming off our photo boat. At 26 knots (3100 rpm), the 3860 exhibited some motion, but the OceanTrac hull design prevented pounding, while the six-inch-wide chines damped all spray. In tight turns, the boat banked as if on rails, running circles inside the photo boat. Top speed was 32.6 knots at 3500 rpm, with efficient cruise at 20 to 30 knots (2600-3300 rpm). Fuel mileage across that span was just over one nautical mile per gallon (18.5 to 26 gallons per hour), remarkable for a 19,000-pound twin-engine cruiser operating at those speeds.
Credit for the efficiency must be shared between the IPS's bite on undisturbed water and the high technology in the D6's fuel system. Throughout our test, the engines were silky smooth, quiet, clean and "willing." Volvo's turbocharged, intercooled diesels have shown very quick acceleration for at least the past 10 years, but the combination of high-pressure common rail fuel injection and electronic control provides even greater throttle response.
Meanwhile, the engines were whisper-quiet at trawler speeds and well under conversation-drowning level at cruising speeds. Again, credit must be shared, this time between the engines themselves, Regal's careful soundproofing of the engine room, the absence of vibration from the tight and compact IPS drive units, and the fact that they bury much of the sound well behind the boat with the exhaust. By the way, there is virtually no smoke in that exhaust, even on hard acceleration.
Out in the Northeast River, I took over the helm to play with the boat at low speeds. Sure enough, maneuverability was remarkable. Working the electronic throttle and shift I could make the boat spin almost on its center. The boat also backed well using the helm, though reversing direction suddenly revealed some inertia. "It's a nineteen- to twenty-thousand-pound hull," Tom Ruggiero observed. "It still behaves like a boat." My choice in tight quarters would be to use the throttle and shift in the conventional way, rather than the steering.
Beyond the D6 engines and the IPS, the 3860 is all Regal, a boat born of a longtime family-owned company that Woody Jackson said achieved a 92 percent customer satisfaction index last year (his own company's index was 94 percent). It has a comfortable helm that combines Volvo controls with a full suite of RayMarine electronics. The bridgedeck includes a chart table and a large semi-circular lounge to port, with a wet bar and refrigerator aft of the helm.
Below are two cabins with cedar hanging lockers, two heads, a lounge in the saloon and a full galley. The cockpit offers an L-shaped lounge built on a hatch that rises on hydraulic rams to reveal the compact, well designed engine room with D6s, IPS drive units and an 8-kilowatt Kohler genset.
The Regal Commodore 3860 is a far cry from the little plywood wonder that Mead Broaddus built in his barn. Boat design has come a long way in the last half century, and new materials and innovative building techniques continue to produce boats that are faster, quieter and more efficient than ever before. The IPS is the newest system to hit the market, and Volvo has committed millions of dollars on its R&D and testing. At this point, it's still evolving, but it looks as if the initial investment has born fruit.
The base price for a Regal 3860 with D6 400 IPS is the same as for the boat with D6s and conventional V-drives: $427,529. The D6 500 version costs an additional $8,800. The price of the boat used in this story is $463,748. For more information, contact Volvo Penta of the Americas Inc., 1300 Volvo Penta Dr., Chesapeake, VA 23320; 800-522-1959;