In 2004, Mercury Marine offered the SmartCraft Digital Throttle and Shift control system in lieu of conventional remote controls on the largest of its outboards. Since that time, it's become available on many of Mercury's outboards, particularly those with electronic fuel injection, or EFI. Much like a computer's "plug-and-play" components, the modular system allows you unplug the shifter wiring, conduct your work and return the vessel to service quickly.
Locate the negative battery post by setting a 5-16-inch box-end wrench over the nut that holds the negative battery cable's ring terminal on the post. Remove the nut from the battery's negative post and remove the negative battery cable from the battery.
Move your hand around the shift actuator, located just behind the bottom cowl on the port side of the motor. Locate the pigtail plug of the Electronic Shift Control shift actuator wiring harness plugged into the shift actuator. Unplug the ESC shift control actuator wiring harness, write on a pre-wired paper tag the information on how the leads of the shift actuator harness are routed to and plug into the engine wiring harness, and attach the tag to the shift harness. Move the engine wiring harness out of the way.
Remove the cottar pin on the rear end of the hitch pin with a pair of needle-nose pliers. Pull the pin out of the bellcrank and actuator. Remove the mounting bolt with a 1/4-inch socket and lift the shift lever from the mounting plate.
Remove the mounting bolt at the opposite end of the mounting plate with a 1/4-inch socket. Lift the shift lever from the mounting plate.
Set the actuator onto the mounting plate as you align the hitch pin assembly. Thread the mounting bolt into its bore and tighten the bolt to 20 foot-pounds with a torque wrench. Set one spacer on each side of the shift piston linkage and connect the piston to the bellcrank and the hitch pin assembly. Insert a cottar pin into the hitch and bend the ends of the pin with pliers.
Read the tag on the shift actuator harness. Route it back to the engine harness according to the directions on the tag and plug the shift actuator harness back into the boat wiring harness. Route and reconnect the shift actuator wiring harness to the engine harness as instructed on the tag attached to the shift actuator wiring harness. Push the shift actuator harness plug into the control box's mounting bracket.
Placing the negative battery cable over the negative battery post. Thread the 5-16-inch battery-post nut onto the battery post. Tighten the nut with the 5-16-inch wrench.
Attach a garden hose to a water source. Screw the remaining end of the garden hose into a motor flushing attachment. Place the "ear muff" shaped ends of the flushing attachment over the motor's raw water intakes, located on the sides of the motor's lower unit.
Turn the water on full force, start the motor and test the shift actuator's adjustment by shifting the motor between its forward, neutral and reverse gears. Shut the motor off, turn the water off and remove the flushing attachment from the motor.
Remove the flushing attachment from the garden hose. Remove the garden hose from the water source and store the hose.
Do not rotate the shift actuator piston while the shift actuator is not in place or you will change the adjusted length of the actuator.