Volvo Penta IPS: The future of Inboard Marine Performance
Article Page 3: The Onboard Experience

The Onboard Experience

Leading marine professionals were invited to be among the first to experience and comment on Volvo Penta’s Inboard Performance System.

One such marine professional shared comments on the experience of running the Tiara Yacht 3800 Open prototype equipped with Volvo Penta-IPS in the waters off Chesapeake, Virginia, during the Fall of 2004.

Comments contributed by Soren Ericson...

The Volvo Penta IPS 500 D6-370 powered 3800 Tiara has forward-facing counter-rotating propellers that “pull” rather than “push,” with their discharge race flowing by a rudder-like support assembly that does double duty handling underwater exhaust discharge.

Part of the reason for the Volvo Penta IPS substantial improvement in propulsion efficiency over inclined-shaft inboards is that the propellers operate in clean, undisturbed water, rather than in the mini-maelstrom stirred up by conventional propeller shaft and struts.

Handling Offshore

Running the Tiara 3800 at cruising speeds offshore was very much like
handling a conventional inboard but with a more reactive helm.

Calibrated to deliver 3.25 turns lock-to-lock, the Volvo Penta IPS helm response was about a turn faster than the conventionally propelled model.

At the helm, the difference was noticeable and appreciated, since any 30-plus-knot boat should be instantly responsive for safety reasons. The term “fingertip control” actually applies in this case—the “steering by wire” allowed me to easily manage a 360-degree turn in 30 seconds with the touch of only two fingers.

While conventional inboard rudders act like brakes, slowing the boat considerably in a hard, prolonged turn, the Volvo Penta IPS powered Tiara slowed considerably less in a turn since propeller thrust is redirected rather than deflected.

The Volvo Penta IPS is designed to operate on any planing, 13-24 degree V-hull with operational speeds up to 45 knots; so this system will be suitable for many smaller and lighter boats as well.

Sport fishing enthusiasts will delight in the Volvo Penta IPS’ astern responsiveness. The boat simply goes where you point it when backing down. It even readily backs downwind without any shift-and-throttle jockeying. No conventional inboard will do that without plenty of throttle-working of opposed engines.

Mid-Range Performance

Mid-range thrust is equally impressive. Getting on plane at 13 knots at 2150 RPM (the same speed at which the conventional inboard planes) was a surprise considering the smaller diameter counter-rotating props.

It is just more evidence of Volvo Penta’s engineering genius that produces so much thrust throughout the entire operating spectrum from so little fuel.

Get-home power on one engine delivers about 8 knots. The hydraulics allow the stopped engine to trail shaft, with the propeller free-wheeling in the surrounding water flow, reducing drag.

There’s no wear- or temperature-related reasons to limit the amount of time you can trail shaft as is the case with some conventional inboards. While running on one engine, less than half a turn on the wheel keeps the boat running straight, meaning you can easily turn into the running engine, unlike most inboards. You can also back toward the running engine, even downwind— try doing that with an inboard!

"More maneuverable than I would have thought possible."