It has long been something of a given in powerboat racing: if you are outboard-powered and want to go fast and win races, you need two-stroke engines. Four-strokes may be fine for "ordinary" boating, they might be clever and sophisticated and use less fuel; however, when it comes to outright speed and such vital statistics as power-to-weight ratios, they simply can't compete.
That conventional wisdom may, however, have been turned on its head in the past few weeks. In a series of early-season ski races on Waikato rivers, a new-generation Yamaha 250hp four-stroke outboard has not only claimed the chequered flag, it has also beaten much larger two-stroke outboards in the process.
The four-stroke outboard, on the back of a Phantom 20 called Smokin', recently won the highly competitive F2 class in the Rollos Marine Yamaha Bridge to Bridge Water Ski Classic. This is a class in which only stock-standard, completely unmodified engines are allowed to compete.
It is also one that had, until then, been dominated by big horsepower two-stroke outboards, many as large as 300hp.
Perhaps even more impressively, Smokin' not only won the race, it also established a new F2 race record, knocking a very impressive five seconds off the previous mark.
That win and the new class record rounded out a fairly spectacular start to the season for the Smokin' team and its 250hp four-stroke. In the Bridge to Bridge feature Long Race, the team (owner/driver Sam Fenwick, observer Chris Wilkins and skiers Kane Carter and Daniel Tuffin) finished an impressive fifth overall, beating several modified outboards generating around 360hp. They also scored a remarkable third placing in the Open Powerboat Sprint (beaten only by a turbine-powered jetboat and a race boat with more than 300hp on the transom).
Moreover, those victories came just a couple of weeks after Smokin' won the Under-19 class in Paeroa. Together, those victories meant Fenwick and his Yamaha F250 SHO also took out the coveted King of the Rivers crown for under-19s.
The F250 SHO (Super High Output) was one of several new V6 Yamaha four-strokes released late last year. Dubbed "game changers" by several in the US marine media, the outboards were claimed to feature "innovative breakthrough technology"; specifically a new "highly advanced" plasma-fusion process for the outboards' cylinder walls. These walls were said to be 60 per cent harder than steel, allowing the company's engineers to create larger cylinder bores, and therefore more displacement, without having to increase the size of the engine.
When Yamaha first released the new four-strokes, it claimed they were stronger, faster and had more torque than their two-stroke rivals. The company also claimed they were significantly lighter.
It seemed an astonishing claim to make and one that, if accurate, would completely alter the power-to weight balance between two-stroke and four-stroke outboards.
Fenwick, for one, is in no doubt that his four-stroke's extra power and torque have made a huge difference to his campaign.
"The engine's power out of the hole is just incredible," he says. "It means we are up and away while our competitors are still struggling to get their skiers out of the hole."
He also believes the 250hp SHO's mid-range to top-end acceleration has been a key factor, especially in his F2 race. "From 5000-6000rpm, the response was instant. On the rare occasions when we had to feather around a tight corner, we were back up to top speed immediately.
"Being able to smash the existing F2 race record by five seconds was a real bonus, too, especially given how close the racing usually is in this class. Last year, all the top boats finished within a second of each other and I know many of them were going even faster this year."
It may be too early to say whether these victories of Fenwick's herald a true paradigm shift in the world of outboard-powered racing. However, should he continue to win, there will no doubt be others keen to see if Yamaha's claim of "lighter, faster, stronger" has potential for them, too.
One thing is for sure. No sensible two-stroke driver will ever look down their nose at a four-stroke rival again.