Re: connecting 2 fish finders
Can [an HDS-5 and an ELITE-7 be connected] directly together with a nmea2000 cable? or do I have to have a whole nmea 2000 system on my boat for them to work?
NMEA-2000 devices are designed to be connected to a NMEA-2000 backbone that has proper power and network resistive terminations. You could experiment with trying to connect two devices directly together, but I don't know of any method to predict the outcome. The chance that it might work could be highly dependent on the devices and exactly how you connected them.
Because the gender of the NMEA-2000 connectors on both devices is the same, you will need to locate or fabricate your own cable. All the premade cables that I know of are male-to-female gender. I do not know of any pre-made cables for the Micro-C wiring devices that have the same gender on both ends and have the proper gender to interconnect the HDS-5 and ELITE-7 devices, so I cannot recommend a source for such a cable.
Assuming you made the proper cable yourself or could find the proper cable already made, you would then be on your own in discovering if the devices communicated properly. Since a NMEA-2000 starter kit only costs about as much as one cable bought separately, I cannot see any advantage in cost for your method as compared to the recommended method. I cannot see any possible advantage to your proposed method of not installing the network in the operation of the devices. Even if it worked, there is not certainty it works as well as the recommended method. To me it seems just as costly, holds no advantage, and seems to undertake a lot of risk because it is completely contrary to the recommended practices.
If you decide to experiment with your method, please let me know the outcome.
If you cannot find the cable you need already being made, it might be because there is little reason to ever use such a cable. You might make an inference from that about whether or not such a method of wiring is commonly used or has any advantages.