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Axius Report

April, 2008

I recently got to test-drive an Axius-equipped 2008 Sea Ray 330 Sundancer, and all I can say is that it was incredible! I was blown away by how nicely everything worked, and am still grinning from ear to ear as I write this! I can report quite honestly, as I am not relying on Sea Ray advertising to pay for this site.

For starters, the test boat was a 2008 Sea Ray 330 Sundancer that was slipped on the A-Ramp at Captain's Quarters. The boat was equipped with twin 496 Magnum® SeaCores with Bravo III sterndrives and Digital Throttle/Shift (DTS). Each engine was rated at 375 hp., and the Axius system increased the MSRP by a little over ten percent.

If you haven't heard much about the Axius system yet, I'll explain in layman's terms how it works. I should note that there are many technical details associated with the system, and I'll do my best to recall how it worked. At its simplest level, you get a side-mounted joystick that sits to your right at the helm. You can move it forward and backward or side to side to control the movement of the boat. The top of the joystick rotates, enabling you to pirouette the boat with a twist.

To understand how the system works, it helps to understand the components. In a conventional twin sterndrive, each lever has a throttle cable connected to each engine and a shifter attached to each transmission. The steering wheel is mechanically linked to both drive units, so they always move together.

Above, the DTS shifter and Jim Tingle from Sea Ray of Louisville

Adding DTS to the system does several things for you. The shifting is smoother, as it is computer controlled as you move out of the neutral detent. The throttle acts as a rheostat, sending an electronic signal to the engine for servo-controlled throttle control. This makes for a much smoother feel at the helm, as there is no cable friction or slop. There is a "Throttle Only" button to control the throttle without shifting, and a "Sync" button that will synchronize the engines at cruise. Another button on the DTS quadrant allows you to operate both engines with a single lever, as indicated by "1 Lever." There is a "Transfer" option that is not used on this particular boat--you would use this feature if you had another DTS controller at a different location, such as a wing bridge or the stern of a larger vessel.

Using the joystick centers the steering and activates the Axius system for docking. Selecting the "Dock" button, as I understand it, reduces the sensitivity on the joystick control. Unlike a conventional twin, where the sterndrives are linked together, the computerized steering has the capability of steering the Bravo III drive units independently. The drives can move outboard as much as 30 degrees and inboard as much as 15 degrees.

It is pretty easy to visualize how the computer uses joystick inputs to go forward and backward. If you give a slight forward pressure on the joystick, both drives nudge into gear at idle. As you move toward full stick deflection, you command up to 1500 RPMs on each engine. Reverse works the same. Pirouetting the boat is very straightforward. A slight twist of the joystick results in the drives shifting, and a further twist causes the boat to rotate faster. Releasing the joystick stops the input, and the rotation stops as the rotational inertia winds down.

Moving the boat directly to the port or starboard is something that you just can't conventionally do with a pair of sterndrives tied together. Under computer controll, it was easy and brainless! Take a look at this rough diagram to help visualize how it works:

To go to port, all the driver has to do is nudge the joystick to the left. To move faster, a little more pressure to the stick is all that is required. The computer shifts one drive into forward and pivots a sterndrive. The other engine goes into reverse, with its drive pivoted the opposite direction. A force diagram from high-school physics shows that the forward and rearward vectors cancel each other out, but both side components are added to give the boat its sideways movement. The beauty of the system is that all the shifting, steering, and application of power is controlled by the joystick.

This all makes for good theory, but how well does it actually work? On the day of my test, there were two drivers new to the system. The river was at 17 feet, so the test was limited to the slow-speed handling. The first driver, we'll call him "the other skipper" to save ridicule, was a very experienced boater with twenty years of handling twins. By comparison, I've been around boats for a while, too, but have also grown up with video games, aircraft simulators, and remote control helicopters. The experience with video games and RC helicopters gave me a slight advantage in that I am used to finessing electronic controllers to achieve a desired result. Jim Tingle from Sea Ray of Louisville was there to supervise the demo.

For starters, both "the other skipper" and I instinctively used the shifters rather than the joystick to make our first moves at the helm. Was this wrong? We felt that we had more control using what was familiar, but wondered if a new driver would just use the joystick. Both of us even used the shifters for our first ninety degree turn. The other skipper commented that the boat seemed to "leap" when the joystick was moved, and that it could be smoother. He was very smooth using the DTS, but found that twenty years of driving boats made it a little difficult to quickly adapt to the joystick. He commented that the system seemed to do an excessive amount of shifting. Having said all that, he did a fine job handling and maneuvering the boat, both conventionally and with the joystick.

On the other hand, I found the joystick to be very intuitive. While I've been around twins for a while, I found that less experience with boats and more experience with games and RCs helped me to embrace the new technology without interference. I found that a small pressure on the stick would cause the drives to shift out of neutral, and an increasing pressure would make for an increasing application of power to make the boat more responsive. We had an occasional crosswind, which sometimes required more than just a slight pressure on the joystick to control the boat. I found that using lots of finesse was the key to minimizing the shifting and keeping the movements smooth. Fortunately, the Bravo III units shift rather smoothly, so it seemed that you could hear them go into gear almost more than you could feel them using slight pressures. A larger, more sudden input would definitely cause the boat to jump, which I accidentally induced more than once.

I used a Monticello houseboat slipped at the end of the ramp as a reference, and maneuvered the Sundancer around the houseboat, moving forward, moving backward, sliding sideways, and pirouetting just to see what the system would do. None of the movements seemed too jerky, and after just a few minutes, I felt comfortably in control while handling a boat in close quarters that I had never even seen before.

The Mercruiser Zeus and Volvo IPS systems, which have been under development for years, take advantage of pod drives to accomplish the same thing as the Axius system. The advantage of the Axius system is that it can be fitted to sterndrives already in production.

Overall, I think these types of systems will revolutionize the way recreational boaters dock their boats in tight spaces. Will this create a new breed of boaters who are crippled by their reliance on technology? Like with other technologies, I suspect that these systems will only expand the capabilities of new boaters. My wife, who doesn't like docking our convertible, for example, would be comfortable docking this Sundancer after only a few minutes of training. Having see the Axius system in action, I am forever ruined. I will certainly wish I had it the next time I return to my lay-along slip and have to spring in to counter a crosswind.

Until next time, thank you for reading! I would like to especially thank Jim Tingle and Sea Ray of Louisville for providing the opportunity to tryout the new Sundancer.

-Captain Eric



Eric Grubb
Founder, Port KY
Licensed Master

Eric grew up around boats, trading summers on board his parents' Sea Rays for many man-hours of swabbing the decks. He grew up by the little town of Sewickley, Pennsylvania, overlooking the the Dashields Locks and Dam. He has traveled the Great Lakes, Lake Huron's North Channel, Gulf of Mexico and several rivers to include the Ohio, Allegheny, Monongahela, Kanawha, Mohawk (Erie Canal), Tennessee, Tombigbee, Black Warrior and Mobile Rivers.

As a commercial pilot, Eric flies jets and is a flight instructor. He has owned recreational boats ranging from PWCs to most recently, a flybridge convertible that he keeps in a Louisville marina (MM 590). You can also find him with his family on the "Escape Pod," an 18' fishing boat. His most memorable journey was aboard the J. S. Lewis, a 155' towboat in service since 1931.

Eric is a USCG Licensed Master with a Commerical Tow Assistance rating, and is a member of the Sons and Daughters of Pioneer Riverman and the Louisville Sail and Power Squadron. After moving to Louisville, he conceived the idea for Louisville's Port KY website while searching for information to help him become a safer and more knowledgable local boater. He has worked hard over the years to educate other boaters by promoting safety classes through Port KY and by hosting captain's classes and related events.




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