Good customer with a new Formula just spent 5K with a very reputable stereo guy on upgrades,speakers,amps ,subs,etc,all the good stuff. But when the engines are running and it's cranked up there is lots of feedback thru the speakers. He claims low voltage on the batteries and he's not responsible. Both batteries read 13 volts. I am not a stereo guy so I need some input before I call BS. Why would weak batteries cause feedback,wouldn't the system just shut down?

I've seen this problem with altenators that didn't put out enough juice. Did he upgrade the charging system?

He Needs To Separate The Power Wire From The Patch Cords. The Two Running Together Will Create Engine Noise.

Add A 1 Farad Cap That May Wor`k If It Is The Voltage.

This is an 07 Formula 330SS with twin 496's,group 24 starting battery,group 31 house battery,and group 24 for genset starting. Stereo guy wants us to replace the batteries before he comes here to see if there is another problem. I don't mind doing that for a good customer but it's alot of trouble if that can't be the problem. For the record,I'm not involved,the customer contracted with the stereo guy. Both engines start fine,everything else works. Do I call BS on the weak batteries and have him come here and solve the problem?

Tell the stereo guy you'll replace them but if that's not the problem HE owes you the labor for the service!

Do you have a couple batteries you can swap from another boat ? if thats the problem then replace them.

When running the batteries should read more than 13 volts. How many amps (amplifiers) and what kind of wattage are they? A capicator will keep the voltage more even and not suck the battery dry every time the bass hits but I hear your problem is noise when running , correct? If it's feedback only when the engines are running it's a wiring issue. As By U Boy suggested make sure the patch ( rca ) cables are a min of 2 ft from the amp power cables and any other heavy guage power cables that may run through the boat. It could just be a bad rca patch cable. If it sounds ok with the engines off and the batterys are fully charged , I'd suspect the wiring before the batteries or charging system. If while the engines are running and the stereo bumping the voltage goes below 11.5-12 v , then time for an upgrade there too. If I did 5g system for a customer and it had some noise I couldnt leave it like that! Shame on the stereo guy!

I have plenty of batteries in stock,that's not a problem. And swapping them out is just a minor labor issue,no big deal. I guess the question is,is the stereo guy right,can weak batteries cause this feedback,or does he need to do some of the things BY u Boy mentioned?

Good point. Why do they sound good when it's not running? Voltage should be higher when running, right?