Speedo & Tach inaccurate. Depth gauge just flashing too

[Larry 0]

Hey all,

Been lurking as I picked up a 2008 Falcon V this summer and have been foaming at the mouth for warm water.  

Both the speedo and tachometer are not accurate.  They indicate a fractional portion or what's indicated on the sure pass display.  There's also a little silver knob to the right of the steering column that when turned slightly effects what the needles indicate that I have no clue what the purpose of is.  Any clues?

Also, the depth sounder just flashes depths that are far from accurate.  It's not consistently wrong (ie. standard vs metric) and always flashes instead of showing a steady depth.  Previous owner said this can be fixed by cleaning the sensor but the sensor seems pretty clean.  

Thanks for any input.  I've tried searching the forums before posting but have had no luck.  Operator error?  

Cheers!

Larry

Lake Hartwell, GA

Edited March 9, 2020 by Larry

[jtryon 24]

you may have to blow out the speedo tube to fix that.  the tach should be running off engine signal though, so i'm not sure why that would be inaccurate.