I missed this earlier question:
igeorge123 wrote:When I connect the ICON PRO RPM gauge, do I use the isolating device to keep the power from the gauge isolated from the engine network at point 14 in the attachment?
No power isolator is needed because the ICON Pro RPM gauge is not trying to power the network on its drop cable
So George asked it again, in another way:
igeorge123 wrote:When I power the [ICON Pro RPM gauge] with the violet wire will the NMEA-2000 drop cable coming from the gauge harness have 12-Volt on the network connector?
The drop cable from the Evinrude ICON Pro RPM gauge does not try to power the network.
The power connected to the VIOLET wire in the harness for the ICON Pro RPM gauge is just for powering the electronics inside the gauge and for powering any subsequent other ICON gauge that might be connected to the ICON Pro RPM gauge when you construct the private ICON gauge network that daisy-chains all the other ICON gauges to the RPM gauge. But that power is not sent back to the network on the drop cable.
The notion that individual devices on the network will provide the network power is, as far as I know, against NMEA recommendations. Despite that prohibition, a few manufacturers have made devices that think their job is to power the network. Typically this was seen in the very earliest implementations of NMEA-2000 or in products which used NMEA-2000 networking but thought that they would be the only device on the network and needed to power an associated sensor. But mostly this is never done any more.
The situation with using the legacy E-TEC engines and the legacy ICON EST controls in which the GATEWAY module is providing power to the network is another exception to the rule of avoiding a device powering the network. That Evinrude chose to have the GATEWAY module power the NMEA-2000 network may be their implementation of how to get power to the NMEA-2000 network that was controlled by the ignition key switch for installations that were not going to buy the additional ACCESSORY RELAY POWER KIT option
. In the legacy rigging, if you want to get power that comes on with the ignition key switch positions ON and START, you have to buy an extra relay kit. It looks like in the newer ICON II rigging Evinrude built that relay into the control head of the ICON II EST controls, providing a nice source for auxiliary devices to get power that is controlled by the ignition key switch.