Honda Faria Rev Counter / Wiring Loom issue

[Skinner2019]

After some help, I had the boat serviced, whilst the engine was being run after the service we noticed that the revcounter, trim gauge and hour gauge were all off. I opened the back of the dash and moved the wires and they all then started. I stripped the loom that feeds the various gauges but found nothing. I direct wired all to test and all but the revconter (normally when applying power the gauge flickered) worked. I then purchased a replacement revcounter from ebay but I think that might be broken as well. Two questions and apologies for my lack of technical knowledge and language:
Is the circuit a loop type, whereby if the revcounter is not working the tilt guage and hour guage would not receive current?
Is there a way to test a revcounter on a bench?
Many Thanks
Andy

[GuyC]

Gauges normally have a +ve and -ve and a sensor wire. In addition they will also have a +ve for the gauge light.

It will probably be a common +ve feeding the gauges but if one of the gauges fails, it won't affect the power to the others.

I don't know how to test the tacho but you might be able to put a multimeter on the end of the sensor wire, when the engine is running, to see if there is a voltage there but I don't really know. I definitely wouldn't put power to the sensor wire to see whether you can make the needle move, tempting as it may seem.

I think I'd check to see if you have power to the gauge and the -ve is actually connected to -ve.

[Skinner2019]

Thanks GuyC, back to tracing the loom... or I’ll just have to get a professional to look. At risk of the summer disappearing and not getting out on the boat with my electrical prowess. The multimeter was showing low readings at the gauge... wallet out time.