That is the single "wake" wire I was discussing above that installs between the two J-boxes in the overhead.This is what Merc told me I needed with their lastest VV gateway software that would solve my issues. I installed it and it fixed everything.
https://www.ebay.com/itm/184530409686?epid=1534429769&hash=item2af6de98d6:g:J~UAAOSweiZfqxl8
If I remember correctly the single wire connector connects to the Port J-box, the other end connects to the Stbd J-box, and the third connector connects to the 87M0070647 Vessel View adapter harness. Then the 87M0070647 VV adapter harness connects to: the Vessel View interface harnesses, Sys Link Gauge harnesses, and Temperature probe. @RBB 's boat should already have that harness with the single wire.
But - you still need the data cross-over harness under the helm which includes the C-Cruise multiplexer box interface also under the helm.