2016 Sea-Doo RXT-X 300 Review

Beyond the extra power, the RXT-X is a more well-rounded craft

Sea-Doo RXT-X fans got a long-awaited present this year – a boost to a legitimate 300 horsepower. That’s big news for sure, but so too are several more subtle improvements to the familiar performance model, including the addition of the ErgoLock system and a new-and-improved Intelligent Brake and Reverse.

It’s a faster boat, no doubt. But it’s also a more well-rounded competitor.

Competitive Horsepower

The engine in question is the 1630 ACE (for Advanced Combustion Efficiency). No, it’s not a totally new powerplant. It is, in fact, based on the previous 1503 Rotax, with the identical 100mm bore but a new, longer 69.2mm stroke. That change equates to the 9% gain in displacement. Other changes include lighter, yet beefier pistons, with longer skirts, lighter and shorter connecting rods to handle the change in stroke, and a new plasma coating on the cylinder walls rather than the traditional steel sleeves to not only drop weight, but perhaps more importantly, provide better heat transfer.

BRP carved out in the RXT-X by giving the engine a major overhaul.

Rounding out the internal changes are a single overhead cam cylinder head with better shaped combustion chambers, larger injectors, and a new coil-on-plug ignition system that promises almost twice the discharge.

COMPARISON: Read our review of the 2016 Yamaha FX SVHO

To combat high temperatures, the engine gets an additional cooling circuit, as well as larger heat sink and improved intercooler. The latter is made from long-life alloys, and adds sacrificial zinc anodes (added also to water-passage tubes). Keeping score, that’s double the cooling capacity and 2.2-times the efficiency of the previous design. Overall cooling has increased by a third.

All of the engine upgrades result in more power and improved performance.

The supercharger design also gets an update for ’16. The big change is a new compact fan wheel with 32 blades, double that found in the previous model. RPM increases to 47,000 rpm. Component-wise, it sports a thicker shaft, additional clutch washers and bearing packs, and is dynamically balanced before assembly. The takeaway? With these changes, Sea-Doo now advertises the supercharger to be maintenance-free.

ErgoLock Improvements

As to what you can expect from a legit 300 horses under the seat, multiple runs on the Cumberland River during Sea-Doo’s Nashville-based press introduction revealed the RXT-X, technically still in pre-production form, routinely went beyond the 67 mph mark with my light 155-pound load and flat conditions. In fact, it went well beyond, flirting with the 70 mph mark multiple times. More realistic conditions and production tuning may lower that mark, but it’s safe to say Sea-Doo is serious about this boat’s performance.

Any questions about how the RXT-X could compete with the more powerful craft on the market were answered with the new 2016 RXT-X 300.

It’s the delivery of that power, however, that really deserves the most column inches. The midrange is particularly potent, with little-to-no hesitation after crossing wakes or cranking the boat into the hardest turns. Instead, the power simply continues to build, delighting the pure performance rider. In addition to the horsepower bump, pump changes deserve some credit. A 159.5mm impeller and RXP-X-style wear ring keep the pump fully engaged during those maneuvers that may have previously caused it to lose some grip. The end result is just simply power, when and where you need it.

As for the craft’s deep-V hull, as previously shown it can deliver on that engine’s newfound promise. The S3 design walks the line between rough and calm-water master, delivering up a stable, predictable ride when conditions are less than ideal, and yet carving turns worthy of the RXT-X heritage in calmer conditions.

COMPARISON: Read our review of the 2016 Sea-Doo RXP-X 300

For 2016, however, the rider gets additional help in pushing the hull to its potential. That assistance comes in the form of the ErgoLock concept making its way over from the RXP-X. The saddle is now narrower in the middle, with the flared thigh bolsters familiar to fans of the two-seater. Add the RXP-X’s inwardly angled footwell wedges, the width- and tilt-adjustable handlebars, and new grips with flattened palm rests, and you can now use the same technique so successful on the RXP-X, transferring much of the force of aggressive turns away from the weaker upper body to the stronger legs and lower body.

A narrower saddle and inwardly angled footwell wedges allow riders to better use their lower body to control the craft.

Familiar Features

It’s a performance-oriented machine, no doubt, but Sea-Doo continues to keep the X models from being one-trick ponies.

Familiar features include Intelligent Throttle Control, which allows users to select differing acceleration curves – Touring, Sport, or ECO – depending upon how aggressively they want the boat to respond and how much fuel they want to use in the process. You also get the dual, digitally encoded security lanyards, one of which can also govern the craft’s speed, adjustable rear sponsons to tailor the craft’s response, an info-packed and easy-to-read gauge package, and a handy glovebox which increases in size from the ErgoLock treatment.

Storage capacity is considerably higher in 2016, including this new, larger glovebox.

For 2016, riders also get a new-and-improved version of Intelligent Brake & Reverse. Sea-Doo’s heralded system for braking the craft at speed, as well as allowing the craft to start in neutral and be shifted into forward and reverse via throttle and brake lever on the handlebars, iBR stops the craft in 160 less feet than a model without braking. With new motor, actuators, mounting hardware, and redesigned bucket and spoiler, the system also responds much quicker, eliminating much of the lag associated with the previous iBR between its theoretical “gears.”

COMPARISON: Read our review of the 2015 Kawasaki Jet Ski Ultra 310R

Even storage gets a boost for ’16, expanding to 42.8 gallons.

True Competitor

Certainly horsepower will be the primary selling point for the RXT-X 300. Those extra ponies are real, and they make a substantial difference in the boat’s performance. The addition of ErgoLock features, however, can’t be overlooked, as well as the improved response of iBR.

Before 2016, Sea-Doo might have been lagging the competition ever so slightly in this high-performance three-seater category. With the RXT-X 300, that’s no longer the case.