Only on port engine through stereo when running. checked all grounds in engine compartment, engines are grounded both alts putting out same. found loose ground behind stereo but doesn't stop the buzzing. noize level raises with throttle, meaning the more throttle the louder the buzz. Any ideas for things we may have missed?

Try running the ground straight to the battery

Did you just change the spark plug wires?

alternator or plug wires. take of alt belt for a minute and see if noise stops. if not, switch all plug wires and see if noise goes to other engine. there is a capacitor you can add to the alt to cut down on AC whistle.

Plug wires are a year or so old, its a serpentine belt so if i take off belt no water. We did move all the plug wires around but didnt replace any yet. thanks for quick responses

on second thought i guess it wouldnt hurt it to run it for 30-45 seconds with no flow just to listen.

I agree with ground check, for all components. What changed? Is this a new system?

If you have an amplifier make sure all speaker wires and rca cables are not touching or close to power wires. I always run my head unit power directly to the battery on both ground and power, I don't trust the factory wiring.

a simple capacitor is all you need. 50 cent solution.

Instead of running it without a belt and water you could just unplug the alternator. I would unplug it and take off the battery cable to it, to be safe. Also wrap it in some electrical tape so it won't short to something.

thats the pisser, nothing changed, just showed up end of last season.

I like the way you think!