It sounds like the source of the problem is likely the VHF
radio, so the OP should be on the way to things working.
I disagree with the initial assertion: "NMEA 2000: Based on CAN, but why so flaky?"
It isn't. I have installed several networks - no problem. When there are problems it is either a rare failure of a supplier's design (this radio for instance), a failure of the installer's design (e.g. too many or not enough terminators), or an electrical
fault in the devices or circuit. Pretty straightforward. We are dealing with a bus here, which by definition shares the same two signal lines with all devices and all cabling; a failure anywhere can affect the entire system.
One problem is the high cost of proprietary NMEA certification
membership), which has discouraged manufacturers from going that route
. Instead there are many NMEA "compliant" devices which have not been through the extensive official test program (and were developed without access to the proprietary specs). Another is that manufacturers insist on using their own proprietary cable designs instead of the recommended DeviceNet connections. This is a mess created by the manufacturers, both as members of NMEA and as sellers wanting to keep things proprietary. If they would just embrace an open standard and let the competitive chips fall where they may things would be so much better (for us). Personally I have just one device that uses a non-DeviceNet connector, which was the only choice at the time, and will be the last. I will also be more vigilant about certification
, but in truth I have not personally encountered any N2K devices that fail to work as expected.
Another problem with N2K is the extensive use of manufacturers' proprietary sentences, and particularly for calibrating sensors. It seems that no one wants to risk sharing good ideas with competitors. Sheesh.
For most cruising boats N2K is a great solution - simple and reliable if installed correctly, even with multiple suppliers of equipment
. I recognize that folks putting together 50 node systems on powerboats can encounter problems, but that is another level of complexity.