I've got 1 house battery and 1cranking battery...both fully charged brand new. anytime I run my radio I keep getting low battery alarm going off. What gives...can I just clip the wire and if so which one...

Both batteries are interstate

Alternator charging well?

Never heard of a low battery alarm????
Do you have to turn your key on to run the radio???

Don't have to turn key on for radio, turn battery switch to either 1,2 or both then turn radio toggle at helm and push power on head unit...

I'm assuming its low battery alert ? ...it's a high pitch beep and it only does it when radio is on, no other acc triggers it. It will even do it while running ...drives us nuts

Maybe the power at the switch is back feeding something??

I highly doubt its a "low battery alarm." Merc does not have such a thing.
More than likely its something in the wiring causing something in the alarm wiring to ground.
A completed ground circuit is what causes a Merc alarm sensor to set the alarm off.

Mercruiser ECM and PCM 555 controllers has a battery voltage low alarm and it lists as fault # 2 as a diagnostic fault code. The jist of that fault is / warning horn / warning alarm is battery voltage below allowable threshold.

Also has guardian mode that can or will varies as for putting the engine into guardian mode. Also how do you know that you have a low battery alarm - do you have smartcraft gauges ?

With that said the OP never mentioned what he has for a app nor whether if its even a Mercruiser engine or if it a carb or computer control engine plus which controller.

Anyways how can anyone ever give you solid advice because it is a crystal ball guess what you have for a motor app and all the other components that are installed especially ECM or PCM controlled plus is this even a Mercruiser app ?

Also what is a house battery ? Marine apps especially for computer controlled engines need a cranking battery for starting and any thing else ie: like accessories and stereo's use a marine deep cycle battery. .

It's a carbed 522 engine, nothing computer controlled..its has one cranking battery and one deep cycle marine battery. I tested both batteries and they check out fine.

Alternator checks out good to...and it's the worst sounding alarm/ beep ever lol just so high pitched

I thought maybe there was just a wire I could clip from back of radio, or from battery but there no other wire coming from battery.

From post #8 it sounds like you mean the radio has a low battery alarm, not the boat ignition system. If that is the case you will also need to explain in more detail. Guys on here are pretty sharp as far as troubleshooting help is concerned but they can't help without every detail. Good luck.

Yes it's an alarm of some sort that is radio related..not ignition related, it's a pioneer ( can't remember model). The alarm / beep come through the speakers