Voltmeter Gauge Reading

ZoeB · Posted: Tue May 31, 2016 11:05 am Post subject: Voltmeter Gauge Reading

Yesterday on the Zoe B I noticed that my volt gauge was hovering around 12 or slightly above. Typically it sits right in the middle for both idle and when running at 4500 RPMs. Right now at idle it sits in the middle where it always has been, but at 4500 RPMs it drops to close to 12, and has dipped below.

Voltage at the battery pre-start is at ~12.74v
Once started the voltage at battery is at ~14.32v and the gauge is right in the middle.

When I advance the throttle to 4500 RPMs, both in gear and neutral the voltage on the gauge drops. While underway it has bounced and dipped to 12 and slightly below. At the same time voltage at the battery at this time reads ~14.14v.

I have run this test with battery 1 and 2, and then with the selector to both and get the same results. No other switches were in use--bilge pump was turned off.

Can I assume my alternator is working fine based on the reading at the battery, and that it is a gauge issue?

2004 Honda BF75--

Thanks,

Dreamer · Posted: Tue May 31, 2016 11:54 am Post subject:

Robert, Unless you have a house battery that is disconnected from the charging system, and the gauge is hooked to it, I would bet on a bad gauge. The whole system should show charging voltage when underway; somewhere around 14.4v.

BrentB · Posted: Tue May 31, 2016 2:41 pm Post subject:

Is the testing with a load (several items turned on)?

Might try it with running, cabin, cockpit and anchor lights, radio, chartplotter, bilge pumps, other items turned off
record values (no load testing)

When turn everything on
record values (load on testing)

If the values are close then alternator is working
If the values are different analog and digital gauges like you have posted I would replace the analog voltmeter. I was curious on the load and no load numbers that is all

I usually do not run the outboard above 1200 rpms in neutral
Always read it is bad on the motor

ZoeB · Posted: Tue May 31, 2016 4:16 pm Post subject:

Thank you both for your responses.

Both batteries can be used to start the engine in individual mode or tied together. I do not have a dedicated house battery.

I did test voltage it with additional items turned on and there was no difference in the reading.

Typically I do not rev the engine in neutral but wanted see if I got the same result in gear vs. not in gear.

Going to troubleshoot the gauge.

T.R. Bauer · Posted: Tue May 31, 2016 5:12 pm Post subject:

Beat me, but the gauge could cause this. However, I'm not sold on it, as could a dirty ground, corroded connection somewhere, and a multitude of other things. To check if it really is the gauge, unhook the wires from the back and see what your multimeter shows. If it reflects what your gauge is showing, you have something somewhere loose or corroded. If you end up with around 14 volts on the multimeter, it is the gauge.

BrentB · Posted: Tue May 31, 2016 7:32 pm Post subject:

I agree

Clean connections at meter, at the battery and battery cable terminal on OB and tighten

add a little dielectric grease, too