I haven't gone dark on these helpful troubleshooting ideas! Work gets in the way. And as the days tick away without a fix, so does our short season! Thank you, Andrew and Brian, for your 'most recent suggestions. I'm very ignorant and still learning about the networking, so please bear with me! Is the N2K connection device also knows as the backbone? Andrew, you mentioned disconnecting from the Yanmar N2K Tees. There is a connection apparatus (backbone?) in the hanging locker below the cabinet behind the dash electronics which I assume is what you are referring to, but this seems to be Garmin related, not Yanmar. I say that because several of the cables that I can trace run up to the cabinet behind the dash. I don't see any gray wires connected to this. Only black and one yellow. The other wires running to this connection I assume are coming from the engine and GPS antenna devices and are bundled in to spaghetti. I haven't yet been brave enough to separate all those wires to see if I can figure out where they come from. Remember, I'm also trying to troubleshoot lack of GPS signal and awaiting a marine electrician to test the antenna.
Brian, you are correct that there is something wrong with the wiring from the batteries. I haven't been able to completely straighten things out since buying. But it's now down to more of a labeling issue and meter feeds. The battery banks and switches don't jive with the battery meter displays on the Sunpower and dash displays. I think that's unrelated to this problem. I'd be the first to admit if I might have messed up connecting things for the season, but the batteries remained connected in the boat this past winter. So nothing has changed since everything worked last season. You suggest removing the battery isolator from the system. I don't know what a battery isolator is. Can you elaborate? I agree that the Garmin communication cable must be okay since it does work when the thruster battery switch is on.
Jim, I think the Teleflex box is the 560i labeled for Yanmar. But, as you can tell, I'm pretty clueless so double check! I think there's a post somewhere about what the current version was at the time of the post. I just recall that it was higher than version 3.x.
Thanks again to everyone for sharing your ideas!
Chris