posted 04-22-2010 09:29 AM ET (US)
I also have a little bit of understanding of the technology of NMEA-2000, so in assessing this problem the following immediately occurs to me:On the notion that you could make an NMEA-2000 sensor to work with the jack plate, the first thing that occurs to me is how far out of the question this really is. Development of your own NEMA-2000 device is clearly much too large a project. An entirely new device would have to be invented, and the PGN registered with NMEA, and so on. All of that would require an enormous amount of work and expense, probably fifty times more than the cost of buying another gauge from the jack plate maker, not to mention a huge amount of electrical engineering and computer code development, This approach is pointless.
Next, we consider the possibility of adapting some existing NMEA-2000 sensor to connect to the jack plate sensor. This avoids having to invent our own new NMEA-2000 device. At the moment we know nothing at all about the electrical nature of the sensor the manufacturer has provided on the jack plate. It is a mystery. However, we assume somehow we could interface the existing jack plate sensor to be electrically compatible with some existing NMEA-2000 sensor. On this assumption we can proceed further.
We have to figure out what existing NMEA-2000 sensor might be useful. A reasonable choice might be trim tab position sensor. We know that the trim tab sensor in an E-TEC is sending a voltage to the EMM that varies over a certain range. Perhaps we could modify the jack plate sensor to work with mimic this voltage. Since we know nothing about the jack plate, no advice can be offered on adapting it to somehow become compatible with the variable voltage of a certain range needed to feed the EMM. Again, we assume that some type of electrical adaptation could be made between the existing sensor on the jack plate and the required electrical input for the trim sensor. However, I must caution here that the trim sensor is wired into the electrical harness of the E-TEC. The existing trim sensor would have to be disconnected, and the jack plate sensor then would be connected to the trim circuit wiring in the engine.
Now we could display the jack plate level on an NMEA-2000 device, however the data would be sent with the PGN for a the trim position. The device might be configurable to show this data. Perhaps if the device is very configurable you could change the legend of the display from "TRIM" to "JACK PLATE POSITION." This would depend on the capabilities of the display device to be reconfigured. In the I-Command gauges I do not recall any device which could be reconfigured like that. I don't think you can change the LEGEND on the display.
I see a few problems with this approach. First, you have to make some changes to the wiring in the engine which connects directly to the EMM. The EMM is a very expensive component, so be sure you know that you're doing before hooking up anything new to the EMM. Second, you'd lose the trim position indicator. For me the trim position is more important than the jack plate position. I suspect the engine trim is adjusted more often than jack plate position, so losing the engine trim to get the jack plate position does not seem like a good trade. Third, the wiring to the jack plate would of course be external to the engine, and you'd have to route this from the jack plate back to the EMM.