On my R27-OB I mounted it on the side wall just behind the Yamaha controls. I have never wired the white wire and have never had a problem with the NeboLink automatically starting. A guy with a R31 posted this on Facebook TugNuts that should work on your R29.
From Gary Harkins....
I found an electrical point to connect the white wire of the NeboLink that should work on most if not all RT's. The engine monitor screen only has power when the ignition switch is operated. I took the connector off the back of the engine monitor and probed each contact with a voltmeter to find the one that was hot when the ignition switch is operated and dead when it is not operated. I then stripped about 1/4 inch off the end of the white wire and inserted it into that contact. The wires are so fine that the connector can still be slipped back on the engine monitor even with the wire inserted. That makes the white wire hot when the ignition switch is operated and dead when it is not operated. Since the ignition switch needs to be operated to start the engine and remains operated until you shut the boat down, it makes this connection point ideal and extremely simple.