Malibu tests secret engine in Australia's toughest proving ground

To test it, the Albury-based boatmaker handed one of the V8s over to what it believes has Australia's harshest test environment: Myuna Bay Waterski Club.

“When we got an engine out here we said ‘Right, what we want to do is try and break this thing, and put it through the harshest environment we’ve got’,” Malibu Boats Australia driveline engineer Chris Maney said.

“Over all the years I’ve worked here we’ve had one particular spot in Australia where we’ve found the worst environment, so Myuna Bay Waterski Club, we do a lot of work with them.

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“Year after year we’ve had failures, and they’ll be the only customer we get year after year, another set of exhaust manifolds, stainless steel, bang, bang … so we said ‘Let’s put this thing in there’.

“So we’ve been running it at around about six months now, and they love it. We didn’t tell them what size the engine was when they received it, they wanted to know and we just said ‘Don’t worry, just take it, try it’, and that’s actually our 5.3-litre, so we’ve gone from using a 5.7-litre to a General Motors-sourced 5.3," Maney said.

“The thing makes more power than the old 5.7 with its sequentially injected engine, and less fuel, so that thing’s a little ripper.”

The Myuna Bay Waterski Club’s response? “They loved it,” said Maney. “They couldn’t believe how quiet it was … they said they couldn’t even hear the engine run.”

Few details are known despite a test engine being in Australia for about the last 10 months. The new 5.3 is about the same width as the old GM-sourced "350 Monsoon” because of the way the exhaust manifolds wrap, but smaller in other dimensions. It’s direct injected, giving it the ability to produce more horsepower than the 5.7, and more importantly, use less fuel so owners can stay out on the water longer.

It also uses an aluminium block and head, making it lighter than the 5.7.

Skiers who have been pulled by the new donk, fitted to what the Myuna Bay Waterski Club calls its “blue boat”, have raved about it.

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One tester said the engine was so quiet that he could hear his ski around the turn – something that was not possible before. “It took me a couple of passes to realise that it was because the boat was so quiet; I could actually hear the elements around me,” he said.

“It has a really consistent pull that for whatever reason, whatever is happening under there, it gives us a lot of free space, and it gives us a lot of width in the turn, which is really cool.

“It sort of keeps you up quite soft and it’s not dull behind the boat, the moment where you’re having to do extra work to subsidise the lack of power in any way … you still get across the course with a hell of a lot of speed.”

So skiers seem to like the torque of the new donk.

Simon Hill, Malibu Boats Australia’s operations manager, said an engine that was not up to the job of pulling a slalom skier consistently would make things “remarkably difficult”.

“When you [a skier] lean on it [the engine’s torque], you want the power engaged to you so that you can accelerate to the other side of the slalom course,” Hill said. “But once you get there, you don’t want it running away from you, because … that’s where you want to be free of the rope.

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“A boat that doesn’t have the power, doesn’t have the torque to hold onto you is bloody hard to ski behind even if it is showing the same time [to complete the distance] as before.”

That feedback suggests Malibu’s new engine has a flat, wide torque curve right in the sweet spot for towing, making the engine a lot more controllable than the 5.7-litre.

In contrast to the engine it pushes aside, the new donk looks like a marine engine, rather than one robbed from the engine bay of a car. Major changes include moving the raw water pump from a crankshaft-driven unit down the bottom of the engine to a belt-driven one at the top. The design has also reverted to a high-mounted exhaust manifold.

There’s other key changes in the interests of improving the ownership experience.The canister-style oil filter now sits upside-down to prevent oil spilling into the bilge, and the starter motor and alternator are mounted well out of the reach of bilge water. You’ll notice shorter runs of rubber hose, too; that’s to help minimise wear and tear.

“These are things that the servicing people are experiencing every time they service an engine,” Malibu Boats Australia driveline engineer Chris Maney said. “If we can minimise the service time, minimise the mess, it just helps the whole process.”

The new engine was developed with input from McLaren via an engineering outsourcing division that shares its workspace with the Formula 1 team.

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“We went to them and did a lot of research with them [McLaren] on the product before it went into its final design stage,” Maney said. Other input came from US-based Davinci Engineering and Roush Performance.

“They weren’t just working in an office [during the engineering development process],” Maney said. “They were there working with the product, so it’s pretty good to have had those big guys on board with us.”

Last month, Malibu had its third test engine delivered to McLaren. Others are on the dyno bench at GM, testing under a range of running conditions. The new donk has even been subject to altitude testing, with the 3000psi direct injection technology proving its worth in the thinner atmospheric conditions.

Unlike the US, which will do a rolling introduction of the engine across its model range, Malibu Boats Australia chief executive Price Taylor said the new 5.3 would be going in “every single one of our products”, including its entry-level Axis Wake Research-branded boats.

“We’re not the guinea pigs,” Price said.

The new “Gen 5” V8 is based on a GM-sourced long engine fitted with the fuel injection technology. Malibu fits it with a revised intake manifold, exhaust manifold, and the front-end accessory drive system that pushes maintenance points to the top of the engine rather than down at bilge level.

From January 1, the only Malibu boat that the Albury-based boat-maker will offer the old Monsoon 5.7-litre engine in will be the Response TXR.

It will be slightly cheaper for owners to run. Malibu said the engine was equipped to run off E10 ethanol-blended fuel.

Malibu said the engine’s warranty cover would remain at five years.

Pricing? That’s still being worked on, because there are other changes coming to Malibu Australia’s products besides just the engine. More details are expected this month.