Ok so im new to the whole gps speedo deal, my boat has a gaffrig gps gauge with at livorsi gps reciever ontop of the dash and a livorsi tattle tale recall and erase switch, if i turn the key to the on position the gauge jumps to about the 80mph mark then drops to zero, and im getting no speed reading when moving, any suggestion?

I put all new Gaffrig in my boat and it was doing similar things and it turned out that the voltage feeding the speedo was only about 10.5 volts, so I found a new power source at 12.5 vdc and its worked fine. Dont know about mixing brand's thow.

Is there a red sync LED on the antenna, mine has one that tells you are communicating with that guy 26 mile up.

Is this a brand new speedo or is it a few years old? The antenna on the GPS spedos for the first few years were bettery powered, and once the battery wears out in the antenna ther speedo stops working. Some people have been successful in replacing the antena battery and getting it to work again (the battery is cheap, but it takes some soldering to replace).

Livorsi will fix your antenna for around $200.

If this is a new speedo, I'd check all connections and ensure that the antenna is connected correctly.

Are you sure it is a Gaffrig speedo - Livorsi made Gaffrig gauges before a lawsuit forced them to drop the name.