Talkin’ ‘Bout A Revolution
By Capt. Bill Pike — February 2005
Inboard Performance System (IPS) is being billed by Volvo Penta as the most revolutionary development to hit the world of recreational marine propulsion since the introduction of the stern drive (by Volvo Penta, coincidentally) some 40 years ago. Why? First, there’s the free-thinking creativity it took to conceive the system. According to technical project leader Lennart Arvidsson, the original idea for IPS came from submarine periscopes, which vertically transfer and direct sight via motorbike-like handgrips. Why, wondered Arvidsson and his fellow engineers, couldn’t an inboard propulsion system be designed that would transfer power through a vertical shaft and direct it via hydraulics instead of handgrips? “Once we gave up on the hydraulics and went with electronic steering and shifting,” Arvidsson says, “we never looked back.” Then, there’s the engineering that went into IPS:
• Forward-facing counter-rotating propellers are more efficient than conventional props because in the tractor or pulling mode (with the boat going ahead), they encounter clean, solid water, not water disturbed by struts, shafts, or gearcases. Is there a downside to this? Possibly. Forward-facing propellers are virtually unprotected in the tractor mode. There simply are no struts, shafts, or other paraphernalia to protect them.
• Maintenance is easier in some respects. For example, there’s a dual-purpose dipstick just forward of the IPS exhaust inlet elbow. You can use it to check oil levels or pump out approximately 60 percent of the oil to effect a partial oil change. Of course, hauling the boat, removing the drain plug inside the exhaust port of the IPS underwater unit, and draining all or most of the oil makes for a more complete job.
• There’s no aluminum to corrode. The nibral and stainless steel underwater parts of IPS are robust and highly resistant to corrosion as well as marine fouling.
• Steering is electronic. It instantly processes driver input and conveys it to underwater units that articulate broadly at maneuvering speeds (26 degrees on either side of center) and more narrowly for safety at high speeds (12 degrees on either side of center). The upshot? A highly sophisticated, highly responsive, automotive-style progressive steering system that’s easy and fast-turning, especially at slow speeds. Incidentally, should an electronic steering malfunction occur, each IPS comes with a special tool that can be used to center the unit so the boat can return home via twin-screw technique. An autopilot integrated with IPS will soon be offered as well.
• Shifting is electronic. Because of its synchronization with the units’ electronically activated gears, the engine control that I used on our IPS-equipped Cruisers 400 Express is the best one on the market, in my opinion.
• Installation is easier. Because the IPS underwater unit functions as an exhaust pipe, sound and vibration damper, and cooling-water intake, it easily upbolts into a hull that has been prepared with a right-size hole and fiberglass reinforcing ring. No time-consuming installation of exhaust risers, sea strainers, and other ancillary equipage is necessary. Moreover, IPS is more compact and so saves engine space, providing more room for accommodations, tankage, and stowage.
• And finally, there’s the breakaway feature. In a high-speed grounding or a collision situation, IPS’s underwater unit—which may protrude more than comparable inboard props, especially those in tunnels—is designed to simply snap off without opening a hole in the bottom of the boat. The necessity for this sort of thing is obvious, although I think the jury is still out on the long-term practicality and cost of this feature. —B.P.
This article originally appeared in the January 2005 issue of Power & Motoryacht magazine.