On which port of the RUT955 have you connected the E80 ?
The static route I suggested is for trying only, it is a command to be executed in ssh or CLI.
For the VLAN, go to Network->Vlan->Port based. Create a new one (probably 3), set one port of vlan1 to off and set it to untaggeg in the new vlan. Then go to Network->Interfaces, create a new one and edit it, set the phisical interface to eth0.3, disable bridge mode and set the protocol to static with an address in the 10.0.154.0/24 range, create a new firewall zone for this interface only.
Then go to Network->Firewall, allow lan->eth0.3 and eth0.3->lan INPUT and OUTPUT, and enable masquerading.
From Network->Routing->Static routes->Static ipv4 routes add a static route with interface=eth0.3, target=10.0.154.0 netmask=255.255.255.0 gateway=the 10.0.154.x static address assigned above.
With that you can keep the default 192.168.1.0/24 addresses for the RUT, the tablet PC ... and access the Raymarine at 10.0.154.40. No need to fiddle with a 10.0.0.0/? network.