Analog Speedo Not Working But Digital OK

[deanellis1]

I have a 2016 24SD with the large analog speedometer in the middle-right side of the instrument cluster. The analog tach is just to the left. Volvo Penta V8-350. The analog speedo isn't working, but I'm getting a speed when I scroll through the small digital LCD screens on the tach. Because I'm getting a digital speed but not an analog, it makes me think its a gauge configuration issue. The gauges were recently replaced by the dealer for a separate issue. I believe the data (speed, RPM, water temp, air temp, oil press, etc.) comes from a computer in the back and is "daisy-chained" between the gauges. Any experience out there? The dealer is working on it but has not been able to resolve. Related question: Do the digital and analog displays get their signal from the same source?

[AsLan7]

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Analog reading is attained from the pitot tube that hangs off the transom with a VP engine or from the small opening on the lower front of a Merc outdrive. It’s simple air pressure pushed by water (in a boat or by air in an airplane) that pushes a diaphragm in the gauge causing the analog needle to move.

Most of the time, an anolog speedometer not reading correctly is due to a clog of that pitot opening. Carefully use a paper clip to dislodge any debris.

Other causes are a rubber tube failure or it disconnects from the back of the gauge (which normally means water is found under the dash as the water gets pushed up)

Digital readings normally come from GPS.

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[deanellis1]

Thanks - I have cleaned out the pitot tube and that didn't resolve the problem. I'll check for the rubber tube. I don't have a GPS, that I'm aware of...I don't have Perfect Pass or anything similar...is it still possible there's a GPS unit somewhere?

[NautiGirl]

Weird, cleaning out that tube usually fixes it. The speedo on ours wasnt working on our water test. Dealer used a drill bit slightly smaller than the tube to clean it out. It has worked fine since.

Maybe try something larger than a paper clip?

[Big Block Power]

On a couple of my boats I disconnected it at the speedo and blew air backwards through it. Just disconnect it at the pick up. If I didn't get any air flow I just kept working my way back. I have a ton of spare hose from replacing it. It could have a kink in it at the transom too.

[cmattj]

On a couple of my boats I disconnected it at the speedo and blew air backwards through it. Just disconnect it at the pick up. If I didn't get any air flow I just kept working my way back. I have a ton of spare hose from replacing it. It could have a kink in it at the transom too.

Yep I was also wondering if some had the drive off for service recently etc?
My bravos I’ve also use a 1/8 drill bit slowly by hand and pulled wood, and debris from the pick up. Haven’t done that trick on Volvo yet.

[akorcovelos]

+1 on blowing from the dash back with the pickup unhooked. Shop air regulated down to ~10psi worked well for me in the past.