Please sanity check my proposed system

[Steve - Raymarine - Moderator]

This is incorrect, because you are trying to integrated three different interfaces Seatalk 1, Seatalk NG and NMEA 0183. The i70 will not convert the two Seatalk 1 and Seatalk NG interfaces. With engine monitoring, you will want the i70 to communicate Seatalk NG/ NMEA 2000. The i70 can communicate on Seatalk 1 or Seatalk NG
but NOT both.

You would connect the ST4000+ and the ST40 together via Seatalk 1, making sure you leave the RED wire disconnected on the ST4000+ Seatalk connection in order to not back feed power from the Seatalk 1 interface, but you would then connect them to a Seatalk to Seatalk NG converter to the Yellow port establish a Seatalk NG backbone, where the i70 and engine monitoring connection will be connected.

The i70 can not be connected directly to the DeviceNet adapter cable, both the i70 and the DeviceNet adapter cable for Engine data will need to be connected to a Seatalk NG backbone in order to communicate via Seatalk NG/NMEA 2000.

In order to add a NMEA 0183 device into the backbone, you will need another converter, one that converters NMEA 0183 to NMEA 2000, for GPS data like SOG. We don't make such converter but we test with a company call Actisense, they make a converter NGW-1-STNG that will connect to the VHF w/GPS via NMEA 0183 then connect to the Seatalk NG backbone.