UGH! Engine Noise!!! HELP!

[bhectus]

'97 Supersport - I have the dreaded engine noise through my tower speakers and I cannot for the life of me figure out why I am getting it!
Setup - Kenwood KMR-350U head unit, Kenwood KAC-728 300w RMS 2-channel amp running my Kicker KMT-6 tower speakers.
Backround - I had hooked everything up originally on a single battery with my old head unit - the original Clarion radio. Everything worked fine. I wanted to be able to use my Ipod so I bought the new Kenwood radio, and at the same time I installed this I also hooked up a second battery with a Perko switch. Re-wired everything up, and being a dumbass I am since I had power and ground the same color wires, I switched them and immediately blew both 20amp fuses on the amp. Fixed the wiring, put new fuses in, everything played fine in the driveway on batt power only. Hit the lake and...engine noise! I've tried EVERYTHING since that I can think of. Separated pwr and ground so they aren't running together up the side of the hull, went back to single battery to see if this would help, nothing. Changed ground location from block to engine cradle - no dice. The engine whine is the same. I'm wondering if it could be the head unit? The only 2 differences since it was fine on the old head unit are the new head unit, and maybe I did damage to the amp when I switched +/- and blew the fuses? Please help, I'm at my wits end and don't know where else to look without putting the old head unit back in and that is a total PITA.

[bhectus]

Oh, I also tried turning the gain down, didn't help. I also have the interior speakers running off the head unit now and they have -0- engine noise so the issue is definitely with the amp and tower speakers only. This is why it is so frustrating trying to isolate the problem. RCA's are not running near the pwr/grnd wires at all.

[ckdollar]

core-rider said: "No problem man... Forgot to mention if your HU, EQ, etc are not all coming from the same power/ground source as the amps that might cause noise. I had the same problem with my in-boat speakers. Moved the power for the EQ and HU to my distribution lock for the amps and the noise disappeared. Something about long ground loops causes this." on that other post you were talking to him. That might be your problem?

[bhectus]

core-rider said: "No problem man... Forgot to mention if your HU, EQ, etc are not all coming from the same power/ground source as the amps that might cause noise. I had the same problem with my in-boat speakers. Moved the power for the EQ and HU to my distribution lock for the amps and the noise disappeared. Something about long ground loops causes this." on that other post you were talking to him. That might be your problem?

Yeah, that's why I switched back to a single battery to see if that solved the problem but it didn't unfortunately. I'm basically back to my old setup with the exception of the new HU. I didn't have any issues before that. Next weekend I am going to hook up a 5-channel Eclipse amp I have to rule out possible amp damage, if I still have the same noise, then it has to be isolated to the HU. Could it possibly have bad RCA pre-outs?

[xrichard]

When you say you switched back to a single battery, does that mean that power and ground for every component go to the same place...everything runs back directly to the battery including the HU (which would require cutting the OEM power and ground leads and rerouting them)?

[bhectus]

No, the HU power/ground are connected to the factory wires from the dash harness. It was simple plug & play with the exception of the RCA's I hooked up, and the remote turn-on to the amp. So basically no changes there from factory setup.

[xrichard]

FWIW, I've good results running the power and ground for everything to the same location including rewiring the head unit.

[Quick VR-4]

Wire everything to run off the same power/ground. You do not have to use the engine cradle as your ground since a boat has no true ground. Run all power to positive battery and grounds to negative of that same battery. Hopefully that will solve your issue.

[bhectus]

Wire everything to run off the same power/ground. You do not have to use the engine cradle as your ground since a boat has no true ground. Run all power to positive battery and grounds to negative of that same battery. Hopefully that will solve your issue.

Sorry, I wasn't clear enough - The negative cable from the battery is currently grounded to the engine cradle. It was grounded here when I took ownership of the boat, I moved to the block during my noise issue, didn't help, moved it back to the engine cradle. Amplifier ground is wired to - terminal of batt. Amplifier pwr is wired to + terminal, with inline fuse 12" from connection point.

[core-rider]

Do a bit of diagnostics first...

Use an iPod cable directly to the RCA inputs on the amp. If the noise goes away move back through each component from there. If you have an EQ, bypass it, if RCA's are connected straight to the HU, connect the iPod there. These tests will help you figure out what part is causing the noise. More than likely your issue is the HU/EQ power wiring using factory leads. That was my issue with the in-boat speakers.

Try pulling power for the HU/EQ directly from the same power source as the amp/amps. If you have a ditribution block close by wire the HU/EQ there (with fuses of course). If not go directly to the battery powering the amps. Speaker noise typically comes from longer ground loops... Shorter grounds tend to be the problem solver.

Edit: I re-read your original post. You might have noise in the in-boat speakers as well, just can't hear because of less power. The tower speakers are going through an amp that will make noise moree obvious. Do a bit of diagnostics like I mention above and it will narrow down the cause gaurenteed!