Amp gauge

badcrank 777

Contributing Member
Good Morning all,

I have a crazy issue, and need help. I have a 17' runabout with a 110 Johnson outboard. I installed an Faria amp gauge and the usual from stator output to S on the gauge and I on the gauge to the positive battery terminal. All worked just perfect. I could hit the trim motor would show a discharge on the meter, running in the lake would show a small charge going to the battery. All very normal and working perfect.

Decided to install a seperate battery for some accessories, Used a battery isolator. Center terminal of the isolator connected to stator output, terminal 2 to the boat battery terminal 3 to the accessory battery. The terminal 2 of the isolator to the S on the amp gauge, I terminal from the amp gauge to the positive of the boat battery. Just as (or at least I thought) as it was before.

Issue is the gauge will not show any discharge when activating the trim motor, or slight charge when running on the lake.

What am I overlooking.

Thank you

Assuming you mean alternator output vs 'stator', this is what I believe is happening:

Sounds like you have an older diode based battery isolator. If that is the case, when connected as you described, the amp meter CAN'T show any discharge current between the battery and the alternator because of the diodes (inside of the isolator).

I'd say the better fix is to return the diode-based isolator (or sell it) and use the 'newer' ACR technology to charge the accessory battery.

You could also delete the amp meter and just use a voltmeter...
Thank you for this info. What I found was I did not have the amp meter in the correct position. I should have had it from the positive post of the boat battery, and from the other side going to all the 12 V connections on the boat. At that same point connected to output from the isolator. That way when the stator (on my Johnson 110 outboard) is feeding the center post on the isolator I will see a charge going to the battery, and when I operate the trim motor or any function on the boat I will show a discharge, The other side of the Isolator will feed the aux battery that runs accessories. and the two neg post of the two batteries will go to ground being all the negative points on the boat.

You are right this is an old 2 diode isolator, so I have purchased a new ACR from Amazon. And will replace that old isolator.

Thank you so much.