I recently bought a 2003 30 motion with 2.5's. The original owner had a good stereo system in the boat when I bought it.

We took the boat out last weekend and we noticed a humming noise through the stereo as we ran the boat. The more RPM's the louder it got.

What causes this? The batteries are old but seem to be good. If the battery is loosing power would this casue the problem?

Thanks
Don

I call it engine noise. It can be caused by a few different things.Bad patch cords,power wires run to close to speaker wires or patch cords. Low quality componets etc.

It's from your alternator. You can make your own filter from a capacitor or just get one of these.

http://www.crutchfield.com/App/Produ...lter&i=003S25A

we have also seen this happen from a bad ground.

I had this happen when my alternator stopped charging.