2004 Bayliner 175 - Volt, Tach, Speedo, Backlights don’t work

[AllatoonaBayliner175]

Voltage gauge does nothing, tach is stuck at 10 (doesn’t move), speedo does nothing, temp I think is working... oil pressure and fuel bounce to the right when ignition is turned on and the trim gauge responds but slowly. Also, none of the backlights appear to work. I’ve checked all the bulbs as well as removed, cleaned, and reconnected the connections to the gauge posts as well as the harnesses. Speedo appears to only have the vacuum line, but there are no wires lose or not connected (no idea why). This was my grandfathers boat and the Speedo has never worked.
I have a multimeter but I’m not sure what/where/how to test.

 

[mike_i]

what's the status of the battery? Is there a tube for the speedo pickup?

 

[AllatoonaBayliner175]

what's the status of the battery? Is there a tube for the speedo pickup?

I use 2 Deep Cycles and a starting battery with a selector switch. All batteries are good.

Yes, there is a tube for the Speedo. I have tried to clean the port on the drive, but someone else said I could pull the tube off the Speedo and I should be able to blow through it. I haven’t tried that and wasn’t sure if using a compressor to blow through it was OK?