2020 GS22 not getting power to the batteries

[Cosmo]

My 2020 GS22 will not sustain or charge the batteries when running. I’ve already replaced the batteries and the alternator. There is no recharge going to the batteries when it runs. Is there a power control module or some wiring that I can inspect to ensure that the power is getting to the batteries? No fault or warning lights or codes. It’s under warranty but my dealer can’t squeeze me in until late June. And I miss the lake!

[aerojust]

Did you verify that you have 14+ volts at the alternator when the boat is running? In many automobiles, the ECM can command the alternator to turn on or off. Not sure if it is the same with the PCM ECM.

[Cosmo]

The voltage readings are strange. I called Nautique and we are thinking it's a grounding problem. Of course, I can't find any wiring diagrams for this, so I'm chasing wires!

[MLA]

The voltage readings are strange. I called Nautique and we are thinking it's a grounding problem. Of course, I can't find any wiring diagrams for this, so I'm chasing wires!

Ok, this is a start. Where did you measure/observe the strange readings and what was strange about the readings? Follow the voltage and ground paths backwards till the readings are not strange. Problem lies within.

[Cosmo]

My voltmeter, when applied to the alternator and grounded on the engine, showed 27.5 volts, which makes no sense. The voltage at the batteries, which are new, showed 12.4 volts. So frustrating.

[jpwhit]

Do the following readings. Red means the Red meter probe. Black means the black meter probe and post the readings you get. Pay attention to if the reading is positive or negative.

- Red to alternator output, Black to Negative Battery Terminal with engine running. -- Should be between 13.5 and 14.3V
- Red to alternator output, Black to Positive Battery Terminal - Should be close to Zero. If not, bad connection somewhere along positive wiring path
- Red to engine block, Black to Negative Battery Terminal - Should be close to Zero. If not, bad ground connection somewhere between engine and batteries. Check where ground strap attaches to engine as a first step.

[Cosmo]

Thanks. I’ll try that in the AM.

[MLA]

My voltmeter, when applied to the alternator and grounded on the engine, showed 27.5 volts, which makes no sense. The voltage at the batteries, which are new, showed 12.4 volts. So frustrating.

Seems the alternator is charging but is not "seeing" the batteries and is in full-field. I suspect the main battery switch has failed.

[bturner]

27 volts? if that is correct could you have possibly connected the batteries wrong, as in serial? That's the only way I see a properly configured and connected meter getting anywhere near 27 volts. With the alternator charging you should be seeing somewhere about 14.7 - 15 volts tops.

Did this start happening when you summarized the boat or did the boat work properly then all of a sudden with no changes or actions by anyone just start doing this one day?

If it started happening when you or someone else first connected the batteries, I would be going back to look at the connections real carefully. If not then MLA is probably on to something with the switch.

I would also try disconnecting one of the batteries and check that reading again between the battery and ground to see if the voltage is normal. If you're seeing anything more than 15 volts from the alternator when the boat is running in this configuration with one battery, IMO the voltage regulator in the alternator is bad.

[MLA]

Make no mistake. A working regulator CAN produce well over 15V and WILL produce in excess of 15V when there is no load, as in a disconnected battery or broken switch. The down side is, that working regulator wont work for long producing its max output in full-field mode.