Noosa Cat 4100GT (IPS) Review

Issue: March 2006

A World First – In a world first, Noosa Cat has installed Volvo’s latest IPS into a power catamaran.

It had never been done before, so naturally, the Volvo Penta engineers at Guteborg in Sweden were a little cautious about fitting their revolutionary Inboard Performance System (IPS) into a twin-hull boat.

But Noosa Cat’s Wayne Hennig had no doubts he could fit the system successfully to one of his cats.

So he did, and it works perfectly. It’s a world first and now Swedish-based Volvo Penta has given the Australian manufacturer its seal of approval.

The Volvo Penta Inboard Performance System, IPS for short, is a complete package including everything from the steering wheel, controls and engine instrumentation to the propulsion units and the propellers.

Designed for boats with twin-engines, the system had been successfully installed in a number of well-known European brands, along with some Mustang Cruisers on the Gold Coast. But it’s the first time anywhere in the world that the system has been installed in a multi-hull.

The propulsion units are mounted on the underside of the hull, slightly forward of the transom, in specially designed holes integrated in the hull structure.

Unlike shaft drives, the propellers face forward in clean water and direct the backwash parallel to the hull, so that all the power developed drives the boat forward, while counter-rotating twin props cancel out any rotation loss.

In a mono-hull the units emerge either side of the keel, but multi-hulls present different problems.

John Williams from down Lake Macquarie way had ordered a Noosa Cat 4100 (12.26m) with shaft drives, but when he heard about the IPS he was keen to give it a go. John and wife Arom had owned a Grand Banks previously and wanted something with a little more go. They were tired of being left behind by some of their friends in flybridge cruisers on the lake and wanted something that would give the flybridge brigade a bit of stick.

Wayne Hennig said they were always looking for ways to improve their craft. 

“We have tried surface drives, jets, sterndrives and even put foils on the hulls,” he explains. “The surface drives were the fastest and okay in a straight line but the boat wouldn’t turn.” He says while the Volvo Penta IPS is not quite as fast as a surface drive, its handling and manoeuvability are phenomenal.

Wayne Hennig is not giving too much away though. The bottom of each hull was cut off, then inserts were made to mount the underwater system on before the hull was laid up. But the next model will be fully moulded.

The IPS was then married up to a Volvo Penta, 370hp, D6 in each hull, which gives the equivalent of 480hp a side. That’s a heap more horses than the conventional shaft drives or sterndrives can manage. The installation is one of the neatest I have seen. It’s so simple, plus, there’s still plenty of room left in the engine bays.

I have driven some of the European IPS boats and the first Mustang 46 with IPS and was impressed, but I wasn’t prepared for the dramatic change in performance of the Noosa Cat 4100.

There was about a 2m swell running off Mooloolaba the day we ran the test and the big cat loved it. Jumping out of the hole in 6.3 seconds, it settled down to about 24 knots. In most boats this would have been quick enough in the conditions. Although it was handling it well we were falling off the backs of the waves. This wasn’t a problem though – the boat was doing it easily, but it was a little noisy.

Another couple of hundred revs and the boat surged forward at 30 knots and virtually skipped across the top of the swell with an unbelievably soft ride. This was more like it! The faster we went the better the boat liked it and the better the ride. It would make short work of many of those New South Wales bars as the bow comes up when the power is applied, just like an outboard. Try doing that in any ordinary shaft drive diesel!

The throttle response is brilliant and the system has so much torque that a technique of slightly backing off as the boat went over the top of the crest and then accelerating down the other side ironed out the nasty lumps. It also turned flat with just a hint of the turn out that is a characteristic of twin hulls.

The Volvo Penta electronic controls have a positive feel and there is now a beep to indicate when the levers are in neutral.

And who says cats don’t track downhill ? Someone forgot to tell Noosa Cats, the 4100 tracked as straight as a die in the 2m-swell. At one stage during this test I walked away from the helm and there wasn’t the slightest indication the boat was going to broach. Another big plus when coming back in over a river bar.

We found a sweet spot for long distance cruising around 2400rpm and 21 knots. At this speed the engine management system showed the D6s were using about a total of 60lt per hour. There were eight people onboard with 600lt of fuel and 200lt of freshwater. Not a bad load to test the boat. The D6s will rev out to 3550rpm and in flat water the top speed is around 36 knots. In the 2m swell the tachos showed 3300rpm and we recorded a speed of 33.5 knots.

With one engine backed off, the other will not rev above 1500rpm, a safety feature now being reassessed for twin hulls. And if power is lost on one side, the leg can be manually locked in a fore and aft position. John Williams had a big grin on his face during the test and couldn’t wait to take delivery of the boat and drive it home to Lake Macquarie. “After driving this, you wouldn’t want anything else, I can’t wait to give some of those flybridge boys a bit of hurry up,” he laughs.

Arom is still shaking her head at the transition from the Grand Banks to the full on performance of the new boat. There will be one Noosa Cat certainly making a statement on Lake Macquarie this summer.

Following on the success of the 4100GT, Noosa Cats now has a customer who’s ordered a 4400 with the bigger 600 Inboard Performance System installed.

Noosa Cat’s heritage dates back to 1972, when pro fisherman Bruce Harris created Australia’s famous Shark Cat brand of power catamarans. They were big, strong fiberglass boats with unheard of stability and an incredibly soft ride.

After Harris retired his interest in the early 80s, the brand languished for nearly a decade until Wayne Hennig took over the reins in 1990.

Noosa Cat is again writing a new chapter in boating history. Find a nasty ocean bar anywhere along the Australian coast and chances are there’ll be a Noosa Cat close by, either in the hands of the police, rescue groups, serious commercial and recreation fishermen or government authorities.

The IPS was married up to a Volvo Penta, 370hp, D6 in each hull, which gives the equivalent of 480hp a side.

With eight adults onboard the Noosa Cat 4100GT IPS hit 33.5 knots in the rough condition and has a top speed of 36 knots at 3550rpm.

LENGTH: 12.26m
BEAM: 3.5m
DRAFT: 0.52m
WEIGHT: 6800kg
ENGINES: Twin Volvo Penta 370hp; D6 with IPS
FUEL: Two x 540lt
PRICE: $483,000


+ Exception ride; Out-of-hole performance 
– Nothing to report