Voltage to helm gauges, what should it be?

[AllanS]

Bill, not sure what you mean about "same drop across ground buss".

To be more clear, while I can access + and - busses under the helm and cleaned the connections, due to bundling of innumerable wires, I cannot trace them to the helm gauges directly. If I expose the helm gauges, and trace the wires back to its harness, I can identify 4 ground wires, two are 12 gauge that go to each tach, and two are 18 gauge or smaller, but they are all four daisy chained together to all the helm gauges. On the positive side, I see two 18 gauge violet wires that are daisy chained to all the helm gauges, and these appear to be identical to the violet wires coming off the 3-way ignition switches.
The only remaining test I can think to try, which I think I already did but worth trying again, is provide a connection from a known good ground directly to the helm instrument grounds, and test, and do the same for a known good positive connection.

 

[scoflaw]

Check the large plug that goes from the engine to the helm. Called a cannon plug on gassers not sure about yours but there has to be a connection

 

[Skybolt]

Bill, not sure what you mean about "same drop across ground buss".

He means if there are different ground bus bars, use your volt meter and against the same positive source, and measure the voltage between them all, should be the exact same. Also from one bus bar to the next. As well as ohm them out. It should be 0-3 ohms at worst case.

 

[Skybolt]

Check the large plug that goes from the engine to the helm. Called a cannon plug on gassers not sure about yours but there has to be a connection

@AllanS With this year boat there are no plugs with diesels. The engine harness goes straight to the gauges. Depending on PO's there may be a terminal block in between all of this at the helm. Also your system monitor wires will be on a terminal block and they should all be in the same area as the SM wires are in the engine harness also.

 

[ttmott]

Right, I like your thinking (both of you), but I can't really access the 3-way ignition switches from under the helm. I might be able to get to the port switch, but just barely.

Convention is the switches should be dual pole three position. One pole is for start and the other

Check the large plug that goes from the engine to the helm. Called a cannon plug on gassers not sure about yours but there has to be a connection

His gauge, ignition, and cranking power comes through circuit breakers probably in the engine room to the key switches in the cabin then up to the helm and through the helm Ign/Start switches and finally to the gauges. @AllanS said he has battery voltage at the key switches. So that eliminates anything in the engine room. If the Ign/Start switches are original to the boat my bet is they are done or the wire connections on them are done..
Convention is:
Red/Violet wires are primary power to the helm for the engines and engine related instrumentation.
Violet are the switching conductors from switches to end items. Those end items are gauges, fuel solenoid relay, and Systems Monitor.
Yellow/Red are the Start conductors to the starting motors from the Ign/Start switches.

Measure the voltage at the fuel solenoid relay to see if it mirrors the low voltage at the helm. That wire should also be violet.