Fluctuating voltmeter...

[johndoe]

I have 2004 6.2L Mercruiser with Bravo 3... engine has 300 hours, and
I bought it with 100 on it...
Have done most of my own service work, as I am very mechanically inclined, and I am an electronics specialist... I have troubleshoot (shot?) this problem, but can't find the problem..
Voltmeter fluctuates, almost shaking between 11 and 14 volts...(analog guage)... while engine runnning at cruise speed... (3400 rpm and up)
what causes this... I have checked all connections, removed cleaned and replaced...
alternator output is within spec per manual... (I have the service manual)
Batteries all read 12.6 or better... bank one and two...

Had a problem last time out with no power to ignition. key would not turn on any guages or anything.... could not start motor. all accesories worked...
Jumper wire between ignition batery wire and run wire does nothing... even with 12 volts on battery wire... I replaced ignition switch just to be safe...

Manual says there should be no resistance between ignition, and start wires when batteries are disconnected. I show 88.6 Ohms...
When I disconnect engine wiring harness from engine, the resistance goes away... tested slave solenoid... tests good...
what next?

 

[Laddies]

Re: Fluctuating voltmeter...

If you clip a voltmeter on the 2 wires on the back of your voltmeter and run the boat it will tell you if the problem is the gauge of wiring problem I beat on the gauge