Garmin in the weeds, an N2K gripe
Here’s some follow up on Russ Cooper, the Panbot who recently commented that he’s “spent >$10,000 to get an N2K coolant water pressure gauge that works...and still doesn't have one!” Ouch. He has a legitimate gripe, I think, though I doubt the problem is unique to Garmin. You see Russ bought a Bennington 2275RLi with a Yamaha 150 that he’s using on a particularly weedy lake in Ontario. Whereas the Yamaha is sort of NMEA 2000 compliant, he put together the nifty system you can see above (bigger here) and diagramed below. But—cue the Rolling Stones here—you can’t always get what you want, as Russ explains:
After a lot of reviewing on-line, including your great site and several others, I finally purchased a Garmin 4212, GSD22, and connected that to a NMEA 2000 network via Maretron components to get engine data out of my Yamaha F150. One critical piece of data is engine coolant water pressure or temperature. My bay is extremely weedy, and I’ve been having frequent overheat warnings while slow trolling due to a plugged water intake. I figured that by monitoring the numbers, I could determine when a clog had occurred before the motor felt overheated, allowing me to get the clog cleared (by simply turning the motor off for a few seconds.)
Garmin said it supported displaying NMEA PGN 127489, which has within it the fields for coolant water. Yamaha’s ECU puts it into the PGN via an add-on water pressure sensor. So, I figured I could do what I wanted. Well, turns out Garmin doesn’t display all of the fields in PGN 127489. No doubt this is true of other PGNs also. Because of this problem I have had to purchase an additional MFD in the form of a Yamaha digital tachometer to be able to display coolant water pressure {in less than satisfactory bar graph form}.So, now my suggestion. NMEA certification for display devices should be based on a more rigid standard. If a device claims to display a PGN, then it should be able to display all fields within the PGN. If it merely claims to display specific field(s) in a PGN, then that should be their certification level and NMEA should insist that the vendor make that fact clearly known to buyers. For example, Garmin does not advertise what fields they support, only what PGNs they pick fields from.
I don’t know NMEA’s reasoning for grouping fields within PGNs the way they have, but whatever it is we have to agree that a PGN represents a collection. It should not be one collection on one vendors display, yet a different collection on another’s. If there’s an issue with specific fields; either that vendors feel they aren’t being requested or that they’re difficult or cumbersome to accommodate, then NMEA should reconsider what PGN they’re in.
All I know for sure right now is that claims of certification and ability to display specific PGNs is false and misleading to the average, nay even the expert, consumer. This problem is caused by NMEA certification and/or their lack of clarification over what certification means. Since N2K fields are vastly more important than PGNs, vendors’ lack of informing their customers as to what fields can be displayed is leading to purchases which fail to satisfy expected consumer requirements.
FYI, I realized after sending the drawing to Ben that my transducer is connected via a proprietary cable, not NMEA 0183.
Cheers,
Russ