2020 ProXS Discharging to much voltage!

[RustyOutdoors]

Hello hoping to find an answer here
Having an issue suddenly or perhaps just noticing that it appears my alternator is discharging to much.
I recently upgraded to approved lithium batteries in my rig which are unreal.
My problem now is that while running my big motor upwards of 2000rpm my graphs all shut down.
At idle there is no issues all graphs remain on. Change the page to diagnostic so I can watch the voltage and just as I expected, it climbed up to 15v and the graphs shut down for safety.
I have followed every single wire I can and every connection is tight.
My only and best guess at this point is the alternator is discharging too much?

any advice or similar situations would be extremely helpful

serial# 2B689470
2020 pro XS 200

[mactlman]

Look through the old forums. There’s lots of forums on here about overcharge and under-charge on the Mercury alternators

[EuropeanAM]

FIRST and FOREMOST: Connect a known-good AGM battery and verify that the problem is, OR IS NOT still present.