Modern Electronic Remote Engine Controls

ICON Electronic Shift and Throttle Controls for E-TEC

by James W. Hebert

This article describes a modern electronic digital remote engine control system in general and specifically as implemented by the Bombardier Recreational Products Evinrude ICON controls. ICON is not an acronym, but rather a brand identifier for this line of engine electronic products.

ICON controls are a new (c.2009) accessory from Evinrude and replace conventional mechanically linked remote throttle and shift controls with modern, electronic, digitally linked remote throttle and shift controls with added intelligence. Evinrude recently announced that certain 2010 model-year E-TEC V6 engines of 250-HP and 300-HP rating would be available with the option of factory-installed ICON servo actuators and be ready for rigging with ICON remote controls, and that a retrofit kit would be available for V6 engines of 2008 model-year or newer and 150-HP or higher.

The idea of using remote electrically operated devices in place of mechanically linked controls is not particularly new. Outboard motors from the 1960's featured remote electrical operation of their gear shift. Then an electrical actuator moved the clutch and gear in response to remote control input. Today the engine throttle and shift controls remain mechanical in their design, and electrical servo actuators provide the mechanical movement necessary to move throttle plate or shift rod. What has changed considerably is the way these electrical actuators are controlled.

Modern electrically operated controls feature a digital communication network link that operates on just a few wires running between engine and remote controls, and the incorporation of intelligence in the processing of control input from the remote before applying the signal to the motor. These two innovations have permitted the implementation of features in the control system which previously were difficult or awkward to perform, including:

We examine in more detail the two areas of innovation: digital communication and added intelligence. The two are closely related; the first engenders the second.

Digital Communication

Older remote electrical control systems used a non-digital and non-network approach to communication of the signals. Wiring between the remote controls and the electrical actuators was done with individual control wires which performed specific functions. The individual control wires were aggregated into a multi-conductor cable, and conveyed between the remote and the actuators. In modern remote controls like ICON, communication between the remote controls and the actuators is shifted to a command language or protocol. Engine or throttle commands are encoded into serial digital data and sent back and forth between controls and actuators. Further, the digital signal is implemented on a digital data network, which allows connection of multiple devices. This simplifies the wiring and cabling, and allows multiple engines and multiple control stations to all be wired to a single digital control network backbone. From one to five engines can be connected to the ICON digital control network backbone, and up to two ICON control stations as well.

The implementation of the ICON digital control network is based on the very well developed CAN-bus design, which has evolved in the past several decades as a standard for industrial control applications. This takes advantage of existing devices available and used in millions of applications, including most modern automobile engines. The network wiring design allows multiple engines and control stations to all connect to a common network backbone. This vastly simplifies wiring and control.

The ICON engine control network is separated from any NMEA-2000 digital network on the boat. This isolates the engine control network to its own wiring and backbone, increasing network reliability and safety. For even more reliability, the engine control function for EMERGENCY STOP is run on separate, redundant, and dedicated wiring. This further improves reliability.

ICON Components

We now look briefly at the various components of the ICON control system. The ICON digital engine control network consists of two self-terminating hubs to which at least four other devices are attached:

This isolated engine control network is called the ESM bus. In multiple engine installations up to five engines can be attached to the ESM bus. In multiple control station installations, up to two control stations can be attached to the ESM bus. We describe briefly the function of the four types of attached devices and show their implementation in the ICON system.

Electronic Servo Module or ESM

The electronic servo module or ESM is located at the E-TEC engine and installs under the cowling of the engine. The ESM is connected to the ESM bus and to battery power. It communicates with a number of other devices associated with the engine:

Graphic: ICON Electronic Servo Module
ICON Electronic Servo Module (ESM) and its many interconnecting cables.
The ESM installs under the cowling of the E-TEC engine. A small plug-in
identifier module gives each engine a separate digital ID in multi-engine installations.

The electric servo actuators provide the mechanical motion and force to move the engine throttle shaft and gear shift shaft, replacing the normal linkages and cams that perform this function in conventional control systems. The identification plug gives the engine a unique digital identity needed in multiple engine installations. The ESM also connects to the trim and tilt relays. Control of trim and tilt is sent digitally from the helm over the network, eliminating the normal trim-tilt wiring harness. Trim and tilt position is acquired by the EMM from the conventional trim sender rheostat on the engine mounting bracket. Connection to the key switch harness provides control for engine run and normal start-stop functions, as well as emergency stop. Connection to the EMM CAN-bus permits communication with the EMM. This connection supplants the normal NMEA-2000 network connection made to the EMM port.

Electrical Servo Actuators

Electrical servo actuator assemblies replace the conventional mechanical cable linkages to the engine's throttle and shift levers. The servo actuators get their power and control signals from the electronic servo module (ESM). The devices are neatly designed to fit into the existing spaces on E-TEC engines. In this way the E-TEC engine can also be manufactured with conventional controls.

Graphic: Sketch of ICON shift actuator assembly
Shift Actuator Assembly

Graphic: Sketch of ICON throttle actuator assembly
Throttle Actuator Assembly

ICON Gateway Module

The ICON gateway module is typically located near the helm control station. The gateway module communicates with the ESM bus and with the following attached devices:

Note that for oil tank levels, the I-Command instrumentation system already provides a method of tank level sender using oil tank sender convertor devices. The tank levels on the gateway module are only for fuel tanks.

The gateway module passes engine parameters from the ESM bus to the NMEA-2000 network so that they can be used with instruments like the I-Command Digital Gauges, or other NMEA-2000 devices that can display engine related parameters. The gateway also isolates the ESM bus from the other NMEA-2000 devices on the vessel network, keeping their data and network traffic off the ESM bus network. The gateway module also acts as an electronic interface to remote tank level senders for fuel tanks. The interface to tank level senders uses the general electrical standard where a variable resistance (rheostat) controls current flow in proportion to tank level.

Graphic: ICON Gateway module
ICON Gateway module. This module provides a gateway between the ESM network
and the vessel's NMEA-2000 network. It also integrates conventional
resistive fuel tank level senders to the network.

ICON Throttle, Shift, and Trim Control

The ICON throttle, shift, and trim controls are housed in an attractive top-mounting control assembly which is typically located at the helm control station. It connects to the ESM bus and also to the Master Power Key Switch. Through its various levers, buttons, and switches the helmsman inputs control signals to the system. The assembly also contains signal lamps which announce certain engine functions. The ICON control is available in either single lever for single engine installations, or in dual lever for twin, triple, quad, or five engine installations. The input devices are:

The RPM Tune feature is implemented in the remote throttle, shift, and trim control assembly, and sends a command to the engine to alter speed in one percent increments. This command works throughout the engine speed range, and is not limited to only low speed adjustments, nor does it require special activation or engagement.

Graphic: ICON dual handle controls
ICON Remote Throttle and Shift controls. The dual handle top-mounting control can operate two to five engines.

Graphic: ICON single handle control
ICON Remote Throttle and Shift control. The single handle top-mounting control is used for single engine installations. It can also be expanded to dual stations.

The ICON controls also contains illuminated F-N-R (forward-neutral-reverse) indicators to show gear case position; on dual control models there are dual indicators. When the indicator lights for shift position are illuminated, they also indicate that the control station is active. This is useful in multiple control stations. The dual control model also has a red indicator below the SYNC button that indicates the engine speed synchronization feature is active.

Control input for trim adjustment is done using the two rocker switches PORT and STBD on the control base in twin engine installations. In installations of three to five engines, a separate panel is used for the individual engine trim switches. The port throttle handle rocker switch is a master trim control that moves all engines simultaneously. In single engine installations the throttle handle rocker switch provides trim control input.

Master Power Key Switch

The master power key switch panel is located at the helm control station. It connects to the ESM bus, the ICON controls, and to the ICON power harness. The rectangular panel panel contains:

Photo: ICON dual engine master key switch panel
A master power key switch for dual engines.

The master power key switch supplies power to the ESM bus. The emergency stop signal is carried on an isolated circuit in the ESM bus. The engine start and stop signals are routed to the ICON controls to be encoded as digital data, where they will be sent to the engine on the ESM bus. The E-TEC engine starting solenoid relay is not directly controlled by the key switch, but is actually controlled by the EMM. In this regard the E-TEC engine is particularly well suited to electronic control of its ignition and engine cranking. Even in a single engine installation with standard controls, the operation of the E-TEC electric starter motor is handled by the engine management module (EMM) in response to a input signal from the ignition key, and not by directly wired control as was common in older outboard engines.

In installations of more than two engines, these panels becomes more complex, and multiple panels are used, split according to function. For three, four, or five engine installations one panel is used for a master key and single safety lanyard, and another panel is used for individual sets of engine start and stop switches, up to three, four, or five sets. For installations of three or more engines, a separate TRIM-TILT switch panel is also added. Somewhat surprisingly, the power key switch, engine start and stop, and engine trim control panels become the most complex and variable component in an ICON installation. In all there are 13 different panel components that are used in many combinations to provide these functions for one to five engine installations.

Added Intelligence

By moving all control functions to a digital realm, ICON allows for a digital processor to add features and supervision to the system. Control input from the remote throttle, shift, trim, and other controls is processed and evaluated by the ICON system. Following processing, the control input is used to generate control output signals, which then produce actual movement of the engine controls. While this sounds very modern, it actually is a throwback to earlier times.

Before the implementation of direct acting remote engine controls, control input from the helm was typically conveyed to the engine room as a signal which indicated the desired action. For example, the helm would move the engine speed telegraph from NEUTRAL to SLOW AHEAD. The helm did not directly control the engine, but simply sent the engine room a signal via the telegraph that indicated the desired engine speed. In the engine room the signal was processed by the engineer, who actually performed the adjustments to the engine and gears to implement the helm order that was signaled. To let the helm know the signal was received, the engineer would respond by sending a return signal to the helm from the engine room, acknowledging that the order had been received and processed. ICON is the same type of control system, but digital signals replace the engine telegraph, and stored intelligence in the control system replaces the engine room engineer.

The principal areas in which the ICON controls add supervision are in control of engine speed during shifting and matching of engine speed for synchronization of multiple engines.

Shifting and Engine Speed

The gear case of an outboard motor is not designed to be shifted when transmitting a great deal of power to the propeller shaft nor at high input shaft speeds. Typically shifting to FWD or REV from NEUTRAL is only done at engine idle speed. Shifting to NEUTRAL from FWD or REV may be done at higher speed, but typically the engine shaft input is decelerating when the shift occurs. By their use of a single-handle combined throttle and shift control, existing direct control systems provide a control mechanism that helps avoid making a shift at high throttle settings. However, they still allow a crash shift to be made from FWD to NEUTRAL to REV while the engine speed may be quite high. In an electronic control system like the ICON, a shift from NEUTRAL to FWD or REV can be controlled so that it only occurs at a safe engine speed. This prevents a gear case from being damaged by accidental high-speed shifts.

In the ICON system, whenever the actual engine shift position does not match the setting commanded from the remote controls, the electronic servo module (ESM) moves the engine throttle position to idle, waits for the engine speed to drop below 1,500-RPM, then actuates the shift servo to select the desired gear. After the shift is accomplished, the ESM returns the engine throttle to the setting commanded by the control input.

In the case of a crash shift, the momentum of the boat and the flow of water turning the propeller will cause the engine to take longer to reduce its speed to 1,500-RPM. This will add a time delay to the shift. In traditional mechanical controls, this same situation existed due to the high loading of the gears which in turn created very high effort needed on the shift control. The high effort needed from the operator to shift produced a similar time delay.

In direct control systems, the speed of the shift transition depends on the speed at which the operator moves the control lever, as the lever is directly linked to the gear case mechanism. If the operator makes a slow and lazy movement, the gear shift may be too slow and a gear clash may result. In an electronic shift system like ICON, the speed of the shift transition is always crisply executed by the electrical actuator. When the time comes for a shift, the shift transition is made quickly and with precisely the right amount of throw or movement of the actuator. By making firm and consistent shifts, the control system prevents unnecessary gear clash.

Multiple Engine Control and Synchronization

With more than two engines, an electronic control system can reduce the number of control handle to just two, and, by using a set of rules, provide control for up to five engines. If the dual control handles are set for matching direction, i.e., both FWD, both NEUTRAL, or both REV, the control system assumes all engines are desired. All engines then follow the shift controls in unison. If the dual control handles are set for opposing directions, the control system assumes a maneuver is desired, and only the outer engines are controlled. The middle engine (or engines) stay in neutral, while the outer engines respond to further shift and throttle movement.

When two or more engines are used, maintaining synchronization of the engine speeds can become a tedious job for the helm operator. Electronic control systems can provide synchronization of engine speeds, relieving the operator of this burden, and also doing a more accurate job of matching engine speeds.

Incremental Engine Speed Control

In most every remote throttle control system, engine speed control is proportional to throttle lever movement. To produce very small changes in engine speed requires very small movements of the throttle handle. In certain operating conditions it may be desirable to effect very small changes in engine speed; for example, when trolling lures in angling, or when tuning boat speed on plane to suit certain sea conditions, or to meet certain speed limits a small speed adjustment may be desired. With ICON controls, the control of engine speed in small increments can be adjusted without use of the throttle handles. A rocker pushbutton switch with a +/- legend permits the operator to increase or decrease the engine speed in increments of about one-percent of throttle, or typically about 50 to 100-RPM. A small change in engine speed may be difficult to accomplish by throttle handle movement. The rocker switch input provides a better control surface for making very small changes in engine speed, such as finding the most comfortable ride in rough seas or hitting an exact trolling speed.

Aggregate TRIM-TILT Control

An additional control function provided in the ICON system is a master TRIM-TILT control set. The throttle lever mounted rocker switch for TRIM-TILT control becomes a master control that operates all engines in unison. However, this control system does not have any synchronization feature. That is, there is no automatic system for aligning the tilt of all engines. Such a system would require a very precisely calibrated tilt position indicator system. Unlike the engine speed synchronization, which can use the digital engine speed tachometer signal for feedback, there is no such precise trim position indicator signal available. Engine trim position is derived from an analog voltage produced by a conventional trim position rheostat, and creating precision trim measurements from these sensors would require very careful and elaborate calibration of all engines in a multi-engine system.

Control Transfer

In installations with dual control stations, only one station can be active and in control at a time. To pass control from one station to the other, the position of all the engine control handles must be within five percent of each other. Transfer of control can be initiated with the push of single button. Change of control must be accomplished within five seconds. To provide protection against unintended transfer of control, a more complex button entry sequence can be required. The more complex transfer key sequence, called Station Protect mode, can be useful to prevent someone at the inactive control from inadvertently transferring control. For example, Station Protect could be used when there are inquisitive children aboard.


The transition to a modern digital network for engine controls greatly simplifies rigging. Between helm and engine the following conventional rigging is eliminated:

In place of these many cables is a single network connection cable! While this is a significant reduction of rigging even in a single engine installation, in twin, triple, and greater engine combinations, the reduction in rigging becomes fantastic. A single cable runs between the helm and the stern. A second network hub distributes the network to as many as five engines. Each hub has an internal network termination.

Pictorial diagram of ICON engine rigging.
This rigging diagram shows the ICON network wiring for a single engine with single controls. Only one cable is run from the engines to the controls, greatly simplifying installation.


Information on prices for the ICON system components is available in literature from Evinrude.

Further Discussion

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Copyright © 2010 by James W. Hebert. Unauthorized reproduction prohibited!

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Author: James W. Hebert
This article first appeared January 31, 2010.