boat battery fluctuating voltage!

[Jimbeam76]

Hello everyone new member here. I have been working on a deck boat this summer with a 1996 120hp force outboard to get ready to fish. After rebuilding both carbs, fuel pump and adding a trim switch on the motor I decided a working radio would be nice but after installation I noticed it didn't work well after the motor started. so I started by checking the voltage it was getting and it would jump between 1 to 13 volts. So I checked the battery to see if there was a bad wire between the Radio and battery and battery showed same when running. I have checked the rectifier and cleaned all grounds and have changed battery's with a known good battery. I have ran out of things to check as I am not great with electrical problems. Any help will be appreciated.

 

[Grub54891]

Did you ground your meter to the motor or the battery itself?

 

[Jimbeam76]

Did you ground your meter to the motor or the battery itself?

I set the voltmeter to 20v then put respective ends on the battery terminals but it doesn't seem to matter either way I get the same reading

 

[Silvertip]

Disconnect the accessory feed wire from the battery. Make sure you have only the large red positive battery cable connected. Now start the engine and measure battery voltage. If it is still bouncing around you have a regulator/rectifier issue. If voltage stabilizes at 13-14V the issue is with the "boat" electrical system (accessory feed or accessories).

 

[dingbat]

I set the voltmeter to 20v then put respective ends on the battery terminals but it doesn't seem to matter either way I get the same reading

DC current is directional. Reversing the probes would have changed the readings from positive to negative voltages.

Are you sure your not reading AC instead of DC voltage?

 

[Jimbeam76]

Disconnect the accessory feed wire from the battery. Make sure you have only the large red positive battery cable connected. Now start the engine and measure battery voltage. If it is still bouncing around you have a regulator/rectifier issue. If voltage stabilizes at 13-14V the issue is with the "boat" electrical system (accessory feed or accessories).

Sorry for the late reply. I had hoped to post that the problem was fixed but I have tried as you have just suggested and still achieve the same results without the accessories. So I then replaced the rectifier and there was also no change.

 

[Jimbeam76]

DC current is directional. Reversing the probes would have changed the readings from positive to negative voltages.

Are you sure your not reading AC instead of DC voltage?

Wouldn't that just point to the rectifier not doing its job correctly if I am reading AC current?