The iS suspension system will be especially appreciated by passengers, who don't have the handlebars to hang on to.

The iS suspension system will be especially appreciated by passengers, who don't have the handlebars to hang on to.

The 2009 Sea-Doo GTX Limited iS (and the very similar RXT iS 255) is a technological daydream, a machine so wild that if it were proposed five or six years ago it would have been dismissed as impossible except in fiction. This Sea-Doo is straight out of the movies; Batman's PWC, or one designed for James Bond, depending on your generation. But it was about six years ago that Sea-Doo started working on the technology that infuses GTX iS, and fiction has indeed become fact. The wild adaptive suspension system will cause most of the buzz about the new GTX iS, but of all the innovation on this boat - and there is a lot of it - I think the reverse/brake control is the real story.

iControl You

The heart of the GTX iS is iControl, a computer that integrates a number of functions on the boat, enabling features like Intelligent Brake and Reverse (iBR), my favorite bit of technology. The braking system works like the reverse thrust used to slow a jet aircraft on landing. You pull on the brake lever on the left handlebar, and the iControl throttles back the engine for a split second, directs an electric motor to drop the reverse bucket, and then reapplies the throttle to create reverse thrust, which slows the boat dramatically. To keep the rider from being pitched over the bow, the engine is limited (by iControl) to 3500 rpm when the brake is applied. That's enough power to reduce stopping distance from 55 mph by 33 to 50 percent, according to Sea-Doo ( , compared to a GTX with no braking system. If you simply grab the brake, you will get wet, as a wake of water washes over the cockpit as the bow dips on deceleration. But like brakes on any other vehicle, the iBR can be modulated at the lever, and offers enough control that you can avoid the dousing if you like.

This brake lever also controls the reverse function on the GTX iS. When you start the boat, the system defaults to a "neutral" setting that really works. There is no forward or reverse thrust, so there's no need to have the GTX iS pointed towards open water before pushing the start button. Touch the throttle, and iControl selects forward thrust. Flick the brake lever, and iControl selects reverse. Flick the lever again, and you are back to neutral. All this happens without the driver taking his or her hands off the handlebars, or even looking down. And it's fast and smooth. It took me just a few cycles to get comfortable with the function.


Sea-Doo has tried PWC suspension in the past, with a spring-supported seat on its HX and XP models, but the iS (Intellegent Suspension) is a big leap beyond that effort. Sea-Doo has essentially created a third element of the boat to support the passengers and stowage, and then suspended that element over the convention hull and deck. The suspended portion includes the seat, the handlebars and dash, the footwells and the bow stowage. When you walk around the GTX iS, the obvious indications that this boat is very different include the aluminum suspension arm pivoting out of the boarding platform, and the cavity below the bow stowage area required to accommodate movement of the upper deck. The suspended element is supported by a pair of cast aluminum pivoting arms that connect it to the hull. The front arm is forward of the engine, and is hidden from view. It is mated to a coil spring and a shock absorber located in the bilge.

When you start the GTX iS, the suspension system is activated and the entire upper deck moves up as if to levitate over the boat. This is iControl in action again. There's a small electro-hydraulic motor on the suspension that adjusts spring pre-load and ride height. On start-up it raises the suspension to about two-thirds of its six-inch travel, sensing the weight of the passengers on the seat and adjusting pre-load accordingly. Once underway, iControl monitors the suspension travel, and if the spring bottoms out - due to rough water - it adds pre-load to stiffen the ride. If you slow down or your passenger gets off, pre-load is adjusted for the change suspension action or weight. Leave iS in its auto mode, and iControl constantly adjusts the suspension for water conditions, boat speed, and passenger weight. Or you can switch to manual suspension control, and lock in one of nine settings from soft to firm.

The effect of the iS system is to take the "edge" off of riding in rough water. With four inches of suspension compression available, you are still going to feel the boat dicing through a 12-inch chop. But experienced riders will notice that there is less shock transmitted through the handlebars and footwells, and if you look down you can see the footwells moving within the deck. I got to jump back and forth between a standard GTX and the GTX iS, and when riding on some stiff chop in Pensacola Bay, the difference was obvious. It's even more obvious if you are a passenger, and don't have the advantage of holding the handlebars, or being able to stand up.

Bells and Whistles

The brake and reverse system could not function without electronic throttle control, and the GTX iS has a full drive-by-wire system that is progressive for better low-speed control and linked to a no-wake speed control and a cruise control that can be set to hold the boat at any speed. This cruise control also has a memory, so you don't have to re-set it every time you stop - just pull the throttle and you accelerate to the pre-set speed.

That speed is measured by a built-in GPS system that is also programmed to limit the top speed of the GTX iS to 65 mph. In this case, iControl is "you control." The new Learning Key speed control system also utilizes iControl and the GPS, and allows the owner to set Learning Key parameters to limit speed and the rate of acceleration. The GPS also feeds a speedometer and a compass-heading display (but not a nav system) on the new instrument panel, which moves up and down with the adjustable handlebars.

The GTX iS is 11' 7" long, or about 9" longer than the previous GTX models. The hull is all-new, has a rather deep 22 degrees of deadrise, and is close-molded of a new fiberglass-reinforced material Sea-Doo says reduces the weight of the hull by 50 pounds. Despite the light-weight hull, the GTX iS has a hefty dry weight of 948 pounds, compared to 803 pounds for the 2009 Sea-Doo GTX 215. The powertrain is the only carry-over from a previous Sea-Doo model, the same 1.5-liter, supercharged/intercooled triple used in the RXT-X and rated by Sea-Doo at 255 hp.

Other clever features on the GTX iS include retractable mooring lines that zip back into the deck when released, a small stowage compartment under a cover in the boarding platform, an a hinged seat that rises on gas struts so it does not have to be lifted off for routine service. When you raise the seat, instead of the engine bay you see a cover in the lower deck that must be removed to reach the engine.

I've had two chances to ride the GTX iS, once in an early prototype form (with handlebars wrapped in tape and foam an a piece of PVC pipe for a glove box), and later at the media intro, where I rode a $100,000 hand-built "validation" example. Those boats had a few ill-fitting parts, and some electronic glitches. The iControl stopped working a few times and had to be "re-booted," and Sea-Doo is still fine-tuning the brake and throttle progression, for example. So I want to reserve final judgment on a production boat (scheduled to reach dealers in March).

When it's all working, the suspension does its thing and makes a difference in ride quality that's more than subtle but not exactly dramatic. The new hull is designed to lean into turns, which it does well, but it is also less stable at rest, which may bother owners of the previous, rock-steady GTX models. The brake does make a big difference and when it becomes reflexive, should enhance accident avoidance. But this boat is heavy, and you feel every ounce of that mass below you. The big engine delivers great performance, but it's going to use even more fuel moving a craft this weighty. And a key compromise in accommodating the suspension system is a reduction in stowage capacity from 34.3 gallons on the GTX 215 to just 16.4 gallons for the new GTX iS. The new boat has a larger glove box, but the bow stowage is much smaller, a disappointment for a boat designed for touring.

The GTX Limited iS features two retractable Speed Tie mooring lines that snap back into the hull when released.

The GTX Limited iS features two retractable Speed Tie mooring lines that snap back into the hull when released.

And then there's the price: $16,499, compared to $11,999 for the 2009 GTX 215. What price technology? Apparently it's $4,500.

Written by: Charles Plueddeman
Charles Plueddeman is's outboard, trailer, and PWC expert. He is a former editor at Boating Magazine and contributor to many national publications since 1986.