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rpm gauge not working after new engine installed?

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Fishmaster23

Regular Contributor
The shop claimed the tach is getting a signal, but isn't working. Possibly corroded up is what they said. It did sit outside for 2 months, but I'm not buying it. All the other gauges are working. What powers the rpm gauge and how can I test it?
 
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Fishmaster23 said:
The shop claimed the tach is getting a signal, but isn't working. Possibly corroded up is what they said. It did sit outside for 2 months, but I'm not buying it. All the other gauges are working. What powers the rpm gauge and how can I test it?
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Fishmaster23 said:
Also the oil pressure guage IIRC shows all the way high instead of zero with ignition on engine off.
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The tachometer receives it's power via the ignition key switch while in the run mode. It will be powered by the same means as your other instruments!
The tachometer operates by sensing each ignition triggering event... typically via a grey wire.
Sitting outside should not have (key words "should not have") caused it to NOT work now.

The shop should have seen to it that all was working correctly before handing the boat back to you!

Try pulling the engine harness/hull harness connector apart.
Look at the contact pins.
See if there is any corrosion in there that may prevent full continuity.
 
Gauges reading pegged usually means poor or missing ground to gauges/panel. That would also stop the tach from working. The standard wiring practice from factory is to daisy chain the power and ground connections.
 
Are the gauges typically grounded on the engine harness side or should I remove the steering helm and see what's going on with the connectors behind the gauges to check for clean grounds. etc
 
Fishmaster23 said:
Are the gauges typically grounded on the engine harness side or should I remove the steering helm and see what's going on with the connectors behind the gauges to check for clean grounds. etc
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Per Post #4.... each gauge is connected to +12 and to ground at the panel.
 
It could be an issue of new sending units and old gauges not being compatible. I did find the grey wire it was tight and didn't see any issues.
 
Power is often purple, ground is black. Not necessarily visibly loose connections, but poor crimps to the terminals or corroded connections. A voltmeter would come in handy to assure that there is +12V AT each device, i.e. +12 between +12V screw terminal and the ground one on every device.
 
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