Connection Garmin GPSMAP 431 to SmartCraft?

**radiojon** · 10-15-2012, 01:11 AM

Just bought and installed a simple Garmin GPSMAP 431 model chartplotter and read previously that it was a simple two-wire connection into the SmartCraft speedo. However, when I pulled out the dash today, I saw that the speedo (and tach) connections go into a 6-way junction box. The previous instructions I had read let me to believe that there would be two blue and white wires just "hanging" off the back of the speedo.

So how can I connect the necessary Garmin NMEA 0183 wires into that junction box to interface with the speedo? Or is that not even possible? From what I've read, it seems the NMEA 2k devices require advanced interfaces, but I thought this NMEA 0183 model GPS would connect fairly simply.

Thanks in advance.

- Mark

**ZZ13** · 10-15-2012, 06:47 AM

I wired mine up earlier this year and it was just a simple 2-wire connection. They should be there. If they are not "hanging off", maybe they are already connected to an existing chartplotter so that is why you don't see anything dangling??? Or are there no blue/white wire pairs coming off the speedo at all? If you post a pic of the wires coming off your speedometer, could tell you for sure.

**radiojon** · 10-15-2012, 10:11 AM

Bill - all of the speedo's wires (including the blue/white ones) are bundled together and connected to an end block, which is inserted into one of the ports on the 6-way junction box. I have an empty port open on the junction box; am I supposed to buy a port connector, attach the two GPS wires to it, and then plug it into the box? How would I know which pins in the connector to attach the GPS wires to? There was no previous plotter/GPS on the boat.

Thanks!

**ZZ13** · 10-15-2012, 02:44 PM

Originally Posted by radiojon

Bill - all of the speedo's wires (including the blue/white ones) are bundled together and connected to an end block, which is inserted into one of the ports on the 6-way junction box. I have an empty port open on the junction box; am I supposed to buy a port connector, attach the two GPS wires to it, and then plug it into the box? How would I know which pins in the connector to attach the GPS wires to? There was no previous plotter/GPS on the boat.

Thanks!

Ah, I see. Henry Boyd probably would most likely know the answer to this (whether you can pull those two wires off or if you need to get a special connector). You could try a PM to him if he doesn't ring in here soon. Also, here's a thread where I did my "learning":

http://clubsearay.com/showthread.php...ife?highlight=

Also, do all the wires clearly go into a connector that attaches to the junction box? Or is there a wad of tape there and a chance that the two NMEA wires are still just capped off?

**radiojon** · 10-15-2012, 08:38 PM

Good info, Bill! After reading that thread, I'm convinced that there's a NMEA split off the main speedo harness somewhere that I just didn't see when I first took off the dash. All of the web searches I do for "smartcraft speedometer harness" three ends -- one of which looks like it could be the NMEA connection. So I'll check again when I get back to the boat ... and look a lot closer this time. Thanks!

**ZZ13** · 10-16-2012, 06:21 AM

From the pics in your other thread it looks like you have the Ray215 VHF radio. Is that the case? If so, turn it on and see if the display shows a solid "NMEA" or a flashing "NMEA" followed eventually by a long beep. If its solid that means you have NMEA connected to the VHF radio (not sure where it would be getting GPS data if you don't already have a chartplotter/GPS antenna). If it is flashing, then you don't. Just would be another data point that you might be able to use. Also, if you don't, connect the 431s NMEA to the VHF radio as well. The radio uses NMEA to get lat/long position for a distress call. You can only have one NMEA 0183 source (which would be the 431s) but you can have multiple drops on it (which would be the Smartcraft speedometer and the VHF radio).

**Henry Boyd** · 10-16-2012, 08:07 AM

Bill has just about all of it covered. The NMEA cable is a two wire deal in a black plastic sleeve. It has a two pin plug on one end, be tagged with a white label tape. The installation end will be terminated with black shrink wrap. If there is no NMEA harness, the plug on the main SC Tach harness will be capped. This plug should be on a pigtail about 8" long connected at the tach.

Henry

**radiojon** · 10-16-2012, 04:47 PM

Success!!!!!! It turns out that the NMEA blue/white wires were bundled up alongside the speedo harness and covered with electrical tape; I suppose the installer didn't want the wires to hang freely so they just bunched and wrapped all the loose ends and taped it to the main harness. I removed the tape and - voila! - a blue wire and white wire labeled "NMEA", capped at the end with glue and shrink wrap!!!! I didn't have my wire cutters/ connectors at the time, so I am heading back out to the marina tonight to connect them to my Garmin.

Do the engines need to be running to test the connection and do the setup once I have them connected?? Or can I just turn the ignition breakers/switches to the "on" position?

Thanks again for all of the help! You guys are amazing!

**ZZ13** · 10-16-2012, 07:03 PM

Originally Posted by radiojon

Success!!!!!! It turns out that the NMEA blue/white wires were bundled up alongside the speedo harness and covered with electrical tape; I suppose the installer didn't want the wires to hang freely so they just bunched and wrapped all the loose ends and taped it to the main harness. I removed the tape and - voila! - a blue wire and white wire labeled "NMEA", capped at the end with glue and shrink wrap!!!! I didn't have my wire cutters/ connectors at the time, so I am heading back out to the marina tonight to connect them to my Garmin.

Do the engines need to be running to test the connection and do the setup once I have them connected?? Or can I just turn the ignition breakers/switches to the "on" position?

Thanks again for all of the help! You guys are amazing!

Regarding the connections, I put mating bullet connectors on each end and then plugged them together in case I ever changed my chartplotter. That would make for easier removal. Once you have it all connected turn on your engine breakers and your engine keys. No need to start the engine. Then go into CAL2 of your speedometer and select "yes" when you get to the GPS sensor screen. Then on the next screen select "yes" if you want smartcraft to use GPS speed instead of pitot speed (I do this as my pitot is all plugged up somewhere). To test it, on CAL1 of your speedometer make sure you have the Time/Temp screen turned on. Then turn on your 431s and the speedometer should display that it is updating the time from GPS. If it does, you are golden. There are other screens on the speedometer that let you see distance to the next waypoint and fuel to get to the next waypoint. This is all figured out from data that comes over the NMEA. Distance to waypoint is already on your 431s so that is kinda redundant info. But I use fuel to waypoint all the time.

Note: Smartcraft does not like the GSV and VTG NMEA signatures. So if things don't work go see if you can configure your 431s to turn transmission of them off. Actually, you only need RMB and RMC sigs turned on for the Smartcraft and GLL turned on for the Ray215 VHF. That's all I have turned on in my chartplotter.

**radiojon** · 10-17-2012, 01:15 AM

Made the connections tonight and I think I've got the GPS talking to the SC. I plugged in a waypoint on the GPS and it correctly came through on the SC! I did notice the time field populate, too, but it wasn't the correct time (I don't recall seeing an "updating time from GPS" message) -- maybe there's a time zone setting on the GPS that I didn't set??

For the GPS, the only change I made to the configuration was to change Serial Port 1 from "Garmin Data Transfer" to "NMEA Standard" (the other option was "NMEA High Speed"). There are other settings to change the "NMEA Output Sentences" for Sounder, Route, System, and Garmin, but I am completely confused by all of that and have no clue whether or not to change those! :-)

I was a little disappointed that I couldn't get the water depth, water temp, and a couple of other SmartCraft data items to translate BACK to the GPS. The GPS wiring harness instructions led me to believe that the second wire was for two-way communication, but everything I read on this site said to connect the blue (-) wire from the SC speedo into the GPS common ground -- which is what I did. Will the SC NOT send back data to the GPS (NMEA 0183)? Sounds like the only real benefit for hooking the two together is to send the GPS speed to the SC speedometer to bypass the pitot, right?