This topic has been moved to the
EVINRUDE I-COMMAND, ICON Pro, ICON Touch forum for discussion.
It is hard to give advice specific to your installation of the E-TEC engine without knowing the details, such as what type of side-mount control is used and what wiring harness is used.
In general, there should be access to the IGNITION KEY ACCESSORY circuit (ACCY) on a VIOLET conductor and BLACK conductor that are provided in the wiring harness. The VIOLET conductor will be SWITCHED 12-VOLTS; the BLACK conductor will be ground or negative. These conductors may be provided with ring terminal or perhaps on a connector.
If the ignition key switch is part of the side-mount controls, look for these conductors concealed behind the controls.
If the side-mount controls are the concealed-side-mount controls, the ignition key switch is probably already on your helm dash panel; look for these conductors at the ignition key switch.
Once you have located the VIOLET conductor and BLACK conductor, you can use them to provide power to the ICON RPM gauge. You may have to create your own method of interconnection, using perhaps butt-splices or a connector arrangement of your own invention.
Once you have located the pair of conductors (VIOLET and BLACK), you should be able to route them to your helm dash panel. If they are not long enough, you can extend them using marine-grade wire of the appropriate size with appropriate insulation color.
Since your E-TEC engine is a 2018, I assume you recently purchased it from an authorized Evinrude dealer. Your dealer may be of assistance in helping you find the unseen VIOLET and BLACK conductors.
I recommend you get the installation instructions for the ICON series. See
ICON GAUGE INSTALLATION INSTRUCTIONShttp://www.dealerport.com/dealerport/instructionsheets/PDF/766074.pdf