Accuracy of speedo's

[rwells9999]

I'm amazed to hear some guy's quoting speeds that they THINK that they are doing using the pitot speedo's. I'm sure that if they had a GPS to check it against, they would soon come to the conclusion that they are totaly useless. When I put my new rig together a while ago I didn't bother with em. Even the paddle wheel speedo on my Humminbird shows quite a discrepancy at the top end. So when I see postings for 42mph at 4200rpm I ask myself what size donk has this guy got, maybe hes got his MPH/KMH mixed up.
Robin ???

[adrian]

hi
I use my gps for speed as anything in the water has to be affected by tidal flow and if it gets the odd air bubble who knows how fast they are going .
but maybe your right and got the mph /kph mixed up had to in my way of thinking
anzac

[Simon]

a mates x-91 says 2.6 kmph and the GPS says 5kmph at dst and 50+ kmph v 36 kmph at wot.

on Somerset not quite glassed over.
big error for a fancy finder?????
go figure


simon

ps my hummingbird is just as bad.

[SteveCan]

Hi,

I would be trusting the GPS speed over the Sounder. The Sounder has too many variables to deal with.

Although, my GPS and my sounder (Lowrance X65) are within 10% of each other in the 2000 to 4000 rpm range. I think that's mostly luck, the sounders sensor can be effected so many different ways - how it's mounted, weed etc in the water...

Boat speedo's aren't as reliable as car speedo's I reckon.

Cheers
Steve.