zero volt intermittently

[grooviness]

new experience with my twin df300. looking for help to diagnose the issue. Both engines stop abruptly regardless motion (going slow or planning). The same thing happened at the fresh start at the dock so no overheating of electrical components or motion involved.

Gauges will show 0 Volt for both engines. Dreadful beeping goes on. No messages on Suzuki gauges (other than 0 Volt). Tilt (on engines and remote will not work)
Batteries are fully charged (12.5 or more and it happens also with shore power plugged in)

After repetitive turning on/off battery switches and waiting anywhere from 1 - 20 min voltage shows normal and engines restart with no problems. Underway voltage from alternators show 14.5 or more on both engines.

This is certainly electrical issue but where do I begin ?

[tsturm]

I would start at the Battery(s") make sure terminals are clean & tight then both engine grounds & solenoid connections, then batt switch all clean & tight then the dreaded white wire's?

[grooviness]

Thank you TSturm. I'll get on it today. Somehow I fear that this is not it, for I believe my 2 starting batteries are separate (I'll verify that too) for P and S respectively yet the Voltage drops to zero on both.

[Murray]

https://www.suzukioutboardforum.com/...-power-failure

[tsturm]

Thank you TSturm. I'll get on it today. Somehow I fear that this is not it, for I believe my 2 starting batteries are separate (I'll verify that too) for P and S respectively yet the Voltage drops to zero on both.

Common denominator is batt. S/W?

[artdf175]

read my sticky on the "white wire"
Art
( classic example)

[Moonlighter]

I agree with the comments earlier - likely that the white wire connection is the cause. At least its the first place to look, and fairly quick and easy to quick to do.

Now, whether that is due to a loose/corroded connection of that wire to the start battery or to the battery switch, or, whether the wire itself is corroded internally or otherwise compromised (eg damaged somewhere along its length), you will need to find that white wire and check it over yourself. Art’s sticky thread gives more detailed info if the issue is not at the battery/main switch end.

The white wire powers the ecu’s. With poor or intermittent power supply from that wire, the engines will cut out or simply not run. Or, at best, run badly.

[grooviness]

Checked batteries and all wires connected to batteries. Replaced one suspect terminal but it wasn't it. Battery switches and cables are solid as well.
Murray, thank you for the link. Moving today to find infamous white wire. Sounds a lot like my problem with one exception of engine tilt. In my case tilt on the engines doesn't work either so it maybe powered from the same source (via ECU) .
Stupid question; having two df300 with two starting batteries and two batt switches, is there one white wire or each side (port and stbd) has it's own WW?

[grooviness]

Happy to report that the issue appears to be fixed. Didn't have to go too far. Following white wire I opened small white fuse holder. The rubber seal failed and salt vapor must have got in. One of the fuse pins was corroded with white crust. Pulling it out one pin came out and another broke off. Cleaned holder and replaced 30 amp fuse. Voltage error did not come back. For the record, i have only one white wire on stbd side.
Thank you all very much for help and tips.