no power with new batteries

[seabird_cayman]

I have a 2003 3070 offshore with twin f225.
I was powering up and the port engine would lose RPMs and cut out, I started it back up and it did it again a few more times.. we ran for about 20 mins @ 4500RPMS then stopped and anchored for a swim. we headed back and I pulled back the throttle to grab something in the cuddy, when i came up the port engine was off.... i tried to restart it and it seemed like i had killed the battery.. with the SB engine still running i was happy that i could at least get home until that one died and trying to turn it over also seemed like a dead battery. I put a basic volt tester on all three batteries and it show ok... i had no issues with the house battery, so I switched that to the port engine and still nothing.... i didn't even have enough power to raise the engines.
Those batteries were group 27's. the next day I went and bought 3 x 31D's and stiil nothing... all gauges light up when key is in ignition, yamaha gauge reads 11.8-12v, when i go to turn them over the lights dim out and the started does a couple clicks.. thats it.
TABS - total automatic battery system???

thanks in advance,

Colin

[seabird_cayman]

well the culprit turned out to be a bad main ground.. it didn't look bad but after taking off the cables and sanding them the boat has been running fine and hasn't been drawing any power from the batteries...

[MarkT]

Always a good idea to wire brush the battery cable leads and the battery terminals at the beginning of the season. Good luck with the boat.

[Tclaude]

My 2870 did not have battery boxes installed from the factory, that was the first thing I installed when I got the boat. Keeping the battery connections dry is a must to reduce the chances of corruded connections. The hatch above my battery compartment leaks badly during wash-down. A good preventive maintenence tip, spray all the battery connections down with silicon every chance you get.