Mercury - Single JPI
The concept of the JPI (Joystick Piloting for Inboards) system is simple and has been around a long time. It is, simply stated, a system to coordinate the thrusts of an inboard engine with a bow and stern thruster combined, to control the boat’s movement at the dock or in other tight places where wind, current, or the confines of tight spaces make maneuvering difficult, particularly for the less-experienced boater.
This means that an inboard tow boat can be controlled by a joystick, making docking easy.
Simple-sounding but very complicated software development was needed. And as the digital age came to boat propulsion systems with the widespread use of drive-by-wire applications, all of the ground work was in place for the “mass market” of personal inboard cruisers. Joystick maneuvering in commercial vessels has been around for well over 20 years.
A Reason for Being
While it is not frequently discussed, the greatest fear most boaters have is not being caught in a storm, having their boat sink from under them, or even getting caught in the mystical vortex of the Bermuda Triangle -- it is docking their boat when people are watching.
That pressure-packed situation existed since the dawn of power boating until 2006 -- about 100 years -- when the first joystick boats hit the market. Little wonder, then, that pod drives with joysticks, then sterndrives with joysticks, then outboards with joysticks were warmly embraced.
Indeed, BoatTEST streamed the first videos of what those early joystick systems could deliver and sang their praises -- with good reason. In a single stroke, they eliminated one of the biggest obstacles to boat ownership, perhaps second only to cost.
We Test the Mercury JPI
Our test boat was the Sea Ray SLX-W 230, powered by a single MerCruiser 6.2L 370-hp tow sports engine. But the JPI system is made to work with any single inboard engine MerCruiser boat.
The joystick basically integrates the inboard engine with the bow and stern thrusters combined, to give us full maneuverability. (More about stern thrusters later.)
The JPI system can work with only a single bow thruster which shows how well, and how cost-effective, this solution can be.
Now a couple of operational notes… The typical electric bow thruster is not progressive -- it’s either on or off -- but we can make adjustments to the operation to accommodate this, as we’ll see in a moment.
Secondly, electric thrusters can shut down into a safe mode after heavy use if the electric motor overheats. That said, we pounded on our test unit for nearly 45 minutes and had no such problem. We do not think that overheating is a concern, and we rarely hear of problems with it.
Putting the system to the test, we shifted the controls into neutral and the stick became active as seen by the light ring around the joystick turning green. Now as we moved the joystick, the main engines, and bow thruster in this case, activated to move us sideways as desired. The amber lighted ring validates which way the thrust is moving with its own animated movements.
If the thruster -- which has no variable settings remember -- pushes the bow too far, we can then rotate in the opposite direction just slightly to take the thruster out of the equation, which lets the mains get the boat into the proper alignment.
Electric thrusters are loud, so we could easily judge how much or how little rotation was required to start and stop it. In this manner we could keep our side-slip under control and our hull-side parallel to the dock quite easily.
Mercury limits the amount of power we can push into the system. This is a good idea, and keeps heavy-handed captains in check, but still allows more power when needed to fight a hard crosswind or current. We think it is a well-thought-out setup.
In sum, it offers captains a level of precision that was simply not achievable by the average operator -- particularly an inexperienced operator -- with a conventional inboard manual throttles-and-gears system.
For most owners of single-engine inboard towboats JPI is a welcome addition to any inboard helm and one we were quite impressed with. It allowed exacting precision in a cost-effective alternative to conventional throttle and gear docking.
More to the point, it now creates a new market segment where inboard power becomes much more of a viable option for new boat purchases. A good example of that is our test boat -- Sea Ray’s new inboard-powered wake surfing boat, the SLX-230. It has joystick functionality for a single-engine inboard that is every bit as precise as what we have seen on twin-engine cruisers.
But, applications for JPI are not limited to single-engine sportboats -- single-engine cruising boats can also use the JPI system if they are powered by Mercury or Cummins engines.