I have a brand new 260 Sonic with a Gaffrig GPS system. I don’t have the parts numbers of the unit, but it is an analog speedo using the Gaffrig receiver/antenna.
Anyway, I’m getting conflicting speeds with my GPS compared to friends GPS. This wouldn't be that big of a deal but its about a 5 to 6mph discrepancy. My question is; do wind and current conditions affect its accuracy? Or is it possible it could be malfunctioning?

Any help, links, or information on this subject would be greatly appreciated.
thanx,
JL

Are you both in the same boat at the same time with these units?

I am using a Garmin GP-30.
This is my second unit.
It is a nice, dash mounted unit.
The first one, the display went south.
So I bought a used one (rats) from someone and it reads almost 10 mph slower than the previous one (compared to the Gaffrig speedo).
I wonder if there is any way to calibrate the gps speedo's or if you need to replace the antenna/receiver along with the display unit?

Make sure they are not set for Knots! My digital gaffrig was set this way. I am not sure about the analog ones if they have a selector switch.

Once I set the switch right the Gaffrig and my garmin were right on.

Raypanic, good point. I had the same thing last year.

If that's not it, call Gaffig. Or Livorsi if it is a gaffig by Livorsi.

Good pointRayPanic. Conversion of knots to MPH is: Knots x 1.151=MPH.

No...two different boats with factory installed GPS systems.

I went passed him at a pretty good rate and he said his was reading 74.5mph.
Mine was reading 70mph.

My first test run in the boat ran 76mph, I haven't seen anything above 70 since. It's probably right, I was just hoping to see a little more speed out my boat. I have a handheld GPS to test with this weekend, just thought there might be something I could check before.

Anyone else with any ideas???

Does anyone have the GPS owners manual for this unit? I went to Livorsi's web site, but it just had the same sheet that I received from Sonic which states "refer to the owners manual for troubleshooting"

Thanx

Call Livorsi they will check it and recalibrate it if needed.