Finally installed the speedo last week. Bought it used here on oso. Was supposedly tested from gaffrig. Well when I power it on it goes up to 80 then say 50 then 30 then 0. Is that normal. Also doesnt work. Im using the external signal out from my existing GPS for an antenna. That mite be the problem. Any thoughts.

check that the out put on the gps is set right. It can be changed for different devices.

Very interesting. I guess that would require a book and some reading. I think I can check into that. THANKS

I am having a similar issue with mine. I may have to buy the $220 antenna

I have a 2002 35' Reggie Fountain Special Edition that I have owned since 2002. The conventional speedometer keeps torn up all the time. I am wanting to put a GPS speedometer in my boat. The problem is the inside diameter of the hole in dash where the old speedometer was is 3 3/4 " in diameter and I cannot find any white in color GPS that is that size and the outside needs to be around 4" to cover the GPS hole and be flush with the dash. If anyone has any suggestions or any knowledge of what I can do to make this work please let me know. The GPS needs to read around 120. However, it is not that fast. I have twin 575's that have been update with the 80 hp kit's which make it around 655 hp. Runs a solid 100 MPH all the time. With around 40 gals of fuel, a small almost flat chop and 2 people will run 102-103 mph. I appreciate any help you can provide. Harold

[QUOTE=NancyT;4660732]I have a 2002 35' Reggie Fountain Special Edition that I have owned since 2002. The conventional speedometer keeps torn up all the time. I am wanting to put a GPS speedometer in my boat. The problem is the inside diameter of the hole in dash where the old speedometer was is 3 3/4 " in diameter and I cannot find any white in color GPS that is that size and the outside needs to be around 4" to cover the GPS hole and be flush with the dash.

I have a slightly used white Gaffrig 120 MPH GPS speedometer, the very outer edge measures 3 3/4, it came with a colored trim ring that I reused when I replaced it.

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Here is my view on GPS speedometer. Throw the Speedo out, use the speed readout from your GPS chartplotter and put a usefull gauge in the hole left by the junky speedometer.

Padraig

I have the same size water speedo. I assume you don't have enough room to enlarge the hold for a Monster 4 5/8 guage?? Livorsi makes an adapter bezel that will cover the hold and allow you to run a 3 3/8 speedo.