2020 Alternator Voltage good, dash reading low

[ChicoSteve]

2020 25 LSV, M6Di 170 amp alternator, battery option 3 (automatic charge selector)

So I keep getting a low engine battery alarm. I start everyday with fully charged batteries off the tender.  I have 3 batteries on board. The voltage reading on the engine diagnostics screen while running says 14.4 volts, the dash will start at 12 and drop down to 11 or lower after a couple hours. Then randomly, usually after a couple low engine battery alarms it will jump up on the screen to 13 volts or something. Rarely it will show 14.4. Others with the same boat have said it reads 14 volts on the dash whenever the boat is running. I feel like that should be the case, but I dont know if the battery option 3 with the automatic perko has something to do with it. Maybe a bad ground somewhere? bad connection? bad voltage regulator? Not sure where to start trouble shooting. I've got 100 hours on my boat since late April, and I'm hoping to keep using it through October before asking the dealer to figure it out. I carry a DMM onboard, so I have that at my disposal. 

Anyone with similar problems or advice? Advice greatly appreciated. 

Edited July 21, 2020 by ChicoSteve

[Ronnie]

What position do you run your battery switch in?

Battery one is Starting?

Battery 2 & 3 is accessory?