Anyone out there have any knowledge on GPS Speedo's? In particular, I have an 03, 353 that came equipped with a "regular" speedo and a dash mounted GPS (which will obviously display the GPS speed). It seems that every week I am unclogging or reattaching hoses to get my speedo working. It drives me crazy to have a gage sitting there doing nothing. Now for the real question, Can the GPS speedo use the same GPG antenna as the dash mounted GPS, or will I need two separate antennas? If they can utilize the same, is there some sort of splitter available?

It depends on the manufacturer of the GPS that is allready installed, Most offer a wiring harness that comes out of the GPS that can drive and external display like a Gaffrig gps speedo. A Garmin has it for sure what manufacture do you have? Usually its just 3 wires one for negative positive power and one for the serial signal. I believe the GPS Speedos are set up for NEMA 4800 1 1 baud settings.


P.S. Do a search onthe topic it has be detailed here before.

Thanks for the information. It is a Garmin 128. I will search and see what other info I can find. Thanks

I like to see the full display on the gps map.So i put a gaffrig gps on mine with the tattletale switch .You can still use your colored bezel off your old speedo.I have the garmin 182c and the wiring harness that came with the gps had the external gps wire on it . I would think yours would to. Good Luck

Thanks for the info. How do you like the 182c. I have been looking to upgrade from the 128. It does not have mapping capability. How/where did you mount the 182c. I would like to mount it in the same location as the 128. I believe the mounting hole is the same, but the outside footprint is larger. It will be a very tight fit with the stock formula gages. Has anyone tried this combination?

Pic of GPS

Here you go, It says to use the blue wire NEMA out, If that doesent work try the Brown wire. I had a garmin unit where the manual was wrong. You would also have to go into the setup of the GPS to select the output and communications settings.

Thanks Ray. This diagram will help tremendously. I appreciate your help.

Tesheer, How is this for service? 182c just fits. There was nothing there before. The boat is a 382.

Ask and yea shall receive. Thanks for the information and pic. That answers my question.