|
This article was first published in 2001.
|
You can enjoy some big thrills in a ski boat. Travelling by road, your excitement is suppressed by the lawful speed limit of 110 km/h. On the other hand, there is (on most waterways) no such thing as a speed limit when you're in a boat. The only law you have to worry about are those that relate to physics - namely, when high-speed aerodynamic lift tries to flip the boat over end-for-end! That's not so much fun...
Now let's get one thing straight. Going 178 km/h in a car is moving briskly - doing the same speed in a boat can be considered nothing short of crazy! And that's exactly the speed that Peter Phillips' competition ski boat - Prodigy - can achieve. To give you some comparisons, most recreational trailer-drawn powerboats have a top speed of around 60 km/h while a "normal" ski boat might crack 100 kays an hour...
Yes, that makes Prodigy one awesomely quick bit of gear.
Peter's build up to owning and piloting a boat of such ferociousness has been gradual one. He started off ski racing about eleven years ago, having gained experience in the Social (mixed gender) class. After having successfully tested the waters (sorry!), he then graduated into the Unlimited class - the category for serious punters.
Peter has been building this particular boat - a V-bottomed 19 foot 6 inch Spectra - for around three years. It was picked up with a traditional-style supercharged big block in it - but it was nowhere near fast enough to keep up with other vessels in the Unlimited ski class. Unlimited means unlimited power - and, as you might expect, unlimited money. Indeed, you'll find some interesting drive configurations in the Unlimited category. These range from multiple high horsepower outboards (most commonly Mercurys) to all-out forced-induction V8 thumpers.
Peter tells us that the big block Chev is a good motor to enter into the Unlimited class. They're backed by a heap of aftermarket go-fast gear (out of the 'States), they're tough and - of course - they're thumping big an' torquey! Forced induction is, however, mandatory if you want to be competitive in the class. With this in mind, Peter assembled this 454ci 4-bolt main motor himself. Before anything else, he had to build a bottom-end strong enough to withstand over 1000hp and extended load durations. This called for a steel crank, Carillo rods with ARP bolts and JE 7.0:1 forged slugs. These fellas slide up and down in 30 thou enlarged bores, which take the swept volume out to 468 cubic inches - 7.7 litres!
Atop the fully prep'd block are a pair of Merlin aftermarket (cast iron) heads that contain Crow 1.73 roller rockers, Isky valve springs and Manly Severe Duty valves (described only as "big"), which are opened and closed by a Crow roller cam. This sucker delivers about 650 thou lift, 239 degrees duration and 114 degrees of lobe centre separation. It's all spun thanks to a Rollmaster timing chain.
Once the long motor had been assembled, Peter dropped it off at Johnston's Performance Centre (JPC) for the inlet and exhaust manifolds, turbos, intercooling, fuel injection and - basically - anything else that needed to be done. Starting where the big block leaves off - the exhaust ports - the JPC guys fabricated custom tubular manifolds to channel gasses to a giant pair of outbound fans - truck-based TA45 Garretts! With a little internal re-engineering, these turbos work with 50mm PSR wastegates to generate up to 12 psi boost pressure. Boost
may rise to around 15 psi in the near future - once Peter and his skiers gain enough confidence!
With a compressed intake charge comes increased air temperature - but with all of that water surrounding the hull, there isn't much point in letting nature's supplied water-to-air intercooler go to waste! At the base of the transom - the cavitation plate - there's a pick-up that forces water through the intercooler core as hull speed increases. That hefty heat exchanger is a product of Garrett (designed for a marine application) and it swallows air from a JPC-fabricated top hat that mounts dual 75mm Ford throttle bodies on its forward end. Note that JPC are presently working to put together a new-and-improved intercooler core - the feeling is that cooling efficiency can still be further improved. The whole monstrous assembly sits on modified Edelbrock Victor tunnel ram. And does a boat like this require any blow-off valves? Yep - two of AVO's biggest!
Certainly, there's no reason why you can't run a top automotive programmable ECU in a boat. All the vital inputs are still available - except for road speed... Peter's Prodigy thinks with an Autronic SMC computer, which was installed and tuned by JPC. It's programmed to manage a set of eight Rochester 2015 injectors (in Camira mounts), which suckle from a JPC fuel rail and Paxton pressure regulator. Fuel gets there thanks to two parallel 700hp Bosch pumps and a surge tank supplied by a belt-driven primary pump. Due to the high pressures inside each of those massive combustion chambers, a Bosch hi-energy coil is dedicated to each cylinder - in addition to an Autronic CDI unit. In short, there's plenty of spark!
And it's all needed too. Mechanics and other people in the know predict that this engine should be generating over 1000hp on its present 12 psi boost. Fifteen psi, however, is reputedly able to bump the output up to around 1300 horses!
Scary.
As we all know, a car would have trouble putting this kind of power to the pavement - a boat has trouble putting it to the pond... Backing Peter's hyped big block is a US-sourced Casale V-drive, which takes torque through a 100-series driveshaft and - finally - a Menkins 11¼ x 15 inch pitch propeller. Its twin blades are said to offer superior top-end speed over multi-bladed props. And - with the boat's 6100 rpm-limited 178 km/h top-end - who's gonna argue with that?!
Amazingly, Peter says he could squeeze more speed out of her by fitting different gear ratios into the Casale transmission or by changing the propeller pitch - but, hey, there's that aforementioned 'law' to worry about! Not to mention the concerns of the two poor skiers who get pulled along simultaneously... For now, though, Peter tells us his skiers compete at an average speed of "only" around 130-140 km/h - depending on the circuit.
And he wonders why he doesn't have any "permanent" skiers...
Certainly, Peter competes in the ultimate ski class - the Unlimiteds - but note that he also does it all on a relatively mild budget. Some other competitors have a spare "grenade" engine that's used specifically for tuning and testing. Like most people, however, Peter can't afford that kind of thing - not when the engine he's presently got in service is worth around 40 grand...
But no matter what the budget or the drive configuration - there's one all-important factor that limits any vessel's competitive advantage. It's that aerodynamic fine line that you don't want to step over...
Contact:
JPC
+61 3 9465 2244
