Single JPI
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Mercury Single JPI Mercury Single JPI
Mercury Marine’s new JPI (Joystick Piloting for Inboards) was designed for inboard boats powered by single or dual MerCruiser gasoline or diesel engines. The new JPI system gives inboard-powered boats joystick functionality similar to joystick systems for sterndrives, pods and outboards. JPI pairs inboards with thrusters to create this innovative, simple and stress-reducing option; single-engine JPI utilizes bow and stern thrusters, while dual-engine inboard systems work in tandem with just bow thrusters or both bow and stern thrusters, if desired. Just as in 2006, when the introduction of pod drives for cruising boats, coupled with a joystick, made docking easier than ever before. Now, 11 years later, Mercury Marine has introduced a system for inboards that makes docking just as easy, and less costly… Find out all about it…

Key Features

  • Compatible with gasoline or diesel inboard and tow sport engines
  • Joystick piloting system for both single-inboard boats
  • Compatible with Vetus or Side Power brand thrusters
  • Makes docking and trailering much easier
  • Safely pick up riders
  • Smart tow launch profiles
  • Full 360-degree control

Mercury Single JPI Captain's Report

Mercury Single Joystick Piloting for Inboards cover
This simple-looking joystick provides owners of single-engine inboard propulsion systems cost-effective and innovative joystick maneuvering.
Mercury Single Joystick Piloting for Inboards pic1
The new JPI system delivers precise and simple maneuverability previously unavailable with inboard-powered boats.

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 single bow thruster, or 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.

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.

When pod drives with joysticks were introduced to the recreational boating market more than ten years ago, boating was booming, and consumers happily -- and relatively quickly -- accepted the concept. That has continued to be the case with the ensuing introduction of additional Mercury joystick systems.

We Test the Mercury JPI

Our test boat was the Cruisers Yachts 390 Express Coupe with twin 8.2 L MerCruiser gas engines. But the JPI system is made to work with any single- or twin-engine MerCruiser boat, gas or diesel.

The joystick basically integrates the twin engines with the bow thruster, or even bow and stern thrusters combined, to give us full maneuverability. (More about stern thrusters later.)

Mercury Single Joystick Piloting for Inboards bow thruster
Here we see the effects of the bow thruster as it works in conjunction with the main drives.

The fact that the JPI system can work with only a single bow thruster 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.

Mercury Single Joystick Piloting for Inboards automatic engagement
The joystick automatically engages when the shift levers are moved into neutral. The green ring activates to verify this.
Mercury Single Joystick Piloting for Inboards stick movement
When the stick is moved, the LED ring changes color and indicates the direction the control is vectored to.

If the thruster -- which has no variable settings remembered -- 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.

The Mains

Now while the thruster isn’t progressive, the main engines are… so more movement of the joystick added more power to the mains and we moved faster.

Control Limiting

Mercury takes this progressive topic a step further and adds a button to limit 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.

Old Salts and New Tricks

Having said all of this, veteran twin-engine captains can make their conventionally powered inboard boats practically deal cards in the tightest places and have been doing it for years. But where even they can use some help is when a strong cross current takes the stern in its grip and working the props and throttles is not a solution. It is in this situation that thrusters pay off.

Thruster Only. There’s another cool feature of the Mercury JPI system -- thruster only. While driving, we can press the center button to engage this feature, which allows us to drive on the mains and kick in the bow thruster as we travel along. In this case, the joystick is no longer a joystick, but a toggle switch such as those we find on boats with only a thruster.

Mercury Single Joystick Piloting for Inboards thruster control
Here we see the sticks are still in gear, but we can use the joystick as a thruster control to maneuver around a tight turn.

In this manner, when driving in close confines, we can still activate the thruster with a push to the stick to kick the bow around a tight turn while underway. Or when gliding along a narrow alley in a marina, we can nudge the bow one way or another as needed.

Remember, this is a feature that has to be activated; it’s not automatic, as when the joystick activates just by shifting into neutral. Press a button and then we have thruster only.

Mercury Single Joystick Piloting for Inboards idle
Mercury’s JPI in a single-engine version is being installed in Sea Ray’s new SLX-W 230 wake boat, which is powered by an inboard V-drive engine.


For most owners of twin-engine cruising boats, 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 pod drives.

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 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. Now, single-engine sportboats and cruisers with Mercury power can have total docking control.


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