Furuno go-39

[SharkDave]

Good Morning, my SOG on my recently installed new to me gp-39 is showing incorrect. Usually less than my actual speed. Anybody ever have this issue? Hopefully Wharf Rat will chime in if he sees this. Thanks, SD

 

[SharkDave]

Sorry GP 39 not go

 

[Wharf Rat]

What's your other speed source coming from? A paddlewheel or another GPS SOG?

 

[SharkDave]

Another gps. Not tied together.

 

[Wharf Rat]

The two values should be pretty close to identical; is one set to knots and the other to MPH?

 

[SharkDave]

No both knots. Antenna up in clear spot. Can’t figure it out. Hdg and position are correct also.

 

[SharkDave]

And it’s a large(relatively) discrepancy. I cruise around 8kts and it will vary between 2.5-5kts. Not eveven close. Like it throws up a random number

 

[Wharf Rat]

I've never seen this before, but one question that might point to the issue: What is the date and time on both units? There was a GPS rollover event and the GP39 was one of the units affected and the rollover has caused some issues, including the FA50 AIS; needs SW update to correct. Let me know if it's got like a date of 2002 or something pretty off.

 

[SharkDave]

Ok thanks Wharf. I’ll check it when I can get back down to the boat maybe tomorrow am. Appreciate the info on this.

 

[sdonx]

Post here: Furuno USA Community • Index page

 

[SharkDave]

WharfRat, gp-39 showing a 2018 manufacture date on back of unit.

 

[RCLS2016]

Check that DGPS is turned off and that the GMT time is matching on both units. You may also be able to troubleshoot by calling up the satellite status on each unit and compare the times, & satellite signals. Also is there NMEA data going between the units?

 

[SharkDave]

No nmea bus. Nothing connected.

 

[SharkDave]

I’ll check all that thanks.

 

[SharkDave]

 

[SharkDave]

hey WharfRat, could this be the issue? I’m going to head down to the boat before the heat index tops 100 and check it out or am I wasting my time?

 

[Wharf Rat]

Honestly I doubt it; it's meant to just dampen the update rate so you don't have values that are jumping around; unless someone entered in some crazy value, I don't see how it could give you a consistently incorrect speed over ground. That said, I'd make sure both values are at 0 (no smoothing) as it really is only used by sailors who are trying to compare a steady SOG reference value to their STW paddlewheel when racing.

EDIT: Did you post this on the Furuno forum? Curious what they have recommended.

 

[SharkDave]

No I haven’t messed w the furuno forum yet but plan to if this doesn’t cure my issue. Thanks for your response. I appreciate it. SD