Volvo Penta IPS tested against conventional straight shaft 20 percent faster and 30 percent better fuel economy

How great is the difference between the IPS system and a conventional straight shaft installation? Volvo Penta installed IPS and a conventional straight straight shaft in two identical boats and performed comparative tests.
The boats in Volvo Penta’s test were two Cranchi 41 Mediterranée models – one fitted with twin IPS 500s and the other with twin TAMD63P engines with conventional straight shafts. The engine output was the same in both boats – 2 x 370 horsepower.

Top speed
The boats traveled the same course in both directions and the speed was measured by GPS aboard each boat. The results were as follows:

IPS 500:             Top speed 37 knots
Straight shaft:   Top speed 31 knots

In the test, the IPS boat’s top speed was about 20 percent higher than that of the same boat with a conventional straight shaft installation. To achieve the same top speed as the IPS boat, the boat with the straight shaft would need an additional 150 horsepower per engine, according to Volvo Penta’s calculations.

Both boats began the test at the same time at full throttle from a standing start. The acceleration time needed to reach 25 knots was measured with a stopwatch. The results were as follows:

IPS 500:            13.3 seconds
Straight shaft:  15.3 seconds

The IPS boat achieved planing significantly faster and immediately established a considerable lead. The difference in acceleration times was approximately 15 percent.

Fuel consumption/range
During the test, the boats were driven at a cruising speed of 30 knots and fuel consumption was registered electronically.

IPS 500:                95 liters/hour
Straight shaft:    135 liters/hour
It can be seen that the results were very clear. The fuel consumption of the IPS boat was more than 30 percent lower, which also considerably improves its range between refuelings.

Lower noise
The noise level at the driver’s position was measured with a noise-level meter at cruising speed. The noise level was 7 dBA lower aboard the IPS boat than on the boat with a straight shaft. Given that the decibel scale is logarithmically based, this means that the noise level experienced was nearly halved.

Technical data

                                                      IPS 400                              IPS 500
Crankshaft output:                   310 hp/228 kW                   370 hp/272 kW
Corresponds to 
conventional inboard-
engine output of:
                      approx. 400 hp                   approx. 500 hp
Cylinder volume:                      5.5 l                                     5.5 l
Configuration:                           In-line six-cylinder marine diesel with common rail
Turbocharging:                         Turbo, charge-air cooler    Turbo, compressor charge-air cooler
Gear ratio:                                  1.94:1                                 1.94:1
Voltage:                                      12 or 24 V                          12 or 24 V

Emissions: Will meet future comprehensive emission regulations to be introduced in EU and the US in 2006-2007.

Developed for: Twin installation in planing hulls with a maximum speed from 25 to 45 knots.

Test boats
2 x Cranchi 41 Mediterranée

Length:                      12.2 m (41 ft)
Beam:                          3.84 m (12.6 ft)
Displacement:          Approx. 9.5 tons (20,900 lbs)

Inboard engine with
straight straight shaft:                 TAMD63P 370 hp/2,800 rpm
Inboard Performance System:     IPS 500 370 hp/3,500 rpm

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For further information, please contact Ann-Charlotte Emegård, AB Volvo Penta, phone:
+46 31 66 84 18, E-mail: