Stereo System Wiring??
 

I have a '97 312 formula fastech with twin engines and will be doing some stereo upgrades this winter. But before beginning I have a few "wiring" questions.
Before I start I should state that the boat currently has a aftermarket stereo system (consisting of 2 10" subs running off a mono amp and a 4 channel amp powering 2 6x9's and 2 tweeters) that were installed before I purchased the boat. It was NOT installed by professionals which is the reason I am re-doing most of it (for aesthetics purposes and to make sure the system is set up correctly).
The boat has 2 batteries of which the stereo is currently powered by the port battery. I am unaware if both batteries are connected to the starter or one battery to the starter and one to power other electronics onboard (if anyone knows for sure please clue me in).
Problem is I have noticed a pretty significant "humming" coming out of the speakers when the engines are on and would assume that either they are not grounded properly or I need to install some sort of filter on the wires connecting the amps from the battery. I have noticed the humming is almost non-existent when the engines are off. Would one expect to hear this "humming" noise when the engines are on regardless of which battery the amps are hooked up to or would switching batteries make any difference in the humming? Anyone with stereo expertise have any suggestions on wiring up a pretty basic stereo system with 2 (possibly 3) amps, 4 component speakers, 2 tweeters, and 2 subs?

A lot of factors vary on responding to this post. I will give you 2 senarios first one assumes you use regular class a/ab type of amp. I would run 2 group 29 or 31 deep cycle batteries (depends on how long you play with motors off) connected to the starting battery via a 100 amp voltage sensing relay for charging under way without drawing down your starting battery http://www.defender.com/product.jsp?...6044&id=605576
Run proper sized ground and + cable (fused) to a distribution block near the amps and wire up the amps from there.

Option 2 is running class d amps that are way more efficient and less draw on 1 group 29/31 batt in the same setup.

The buzz you describe is probably bad ground, bad rca's going to the amp, or just a bad amp/ head unit. You say that you still hear the humming with the key off, so i'm not thinking alternator/ignition wires. I would toss everything out and start fresh if it were me. Sure others will chime in

A large CAP at the head-end makes a great filter and helps boost bass response as well. Try connecting a speaker direct to the headend to see if the humming is coming from the head unit or amp.

First off the buzz is probably a ground loop. If the radio is wired through the factory harness, and the amps are wired straight to the battery this will be your problem. Any boat I have seen setup this way will have a hum or buzz when running. Take the power and the ground of the radio back to the battery or where the fuse block is for the amps. That will kill the buzz.

A cap will only help for bass if you are pushing the system to the max. Does not sound like you are trying to set the world on fire so I would not worry about that.

List what you have in the system now. If you have the proper size amps you may not need to add any amps. A good mono for subs and a good four channel for component speakers can make alot of sound set up properly.

Where are the speakers located now? Anything mounted down low in a boat is a waste of a speaker. Subs are best mounted as close to the floor as possible, but you mid/hi speakers need to be up as high as possible. Unless you lay on your floor to listen to the music :)

So give us more info on what you have installed. Link up some pictures if you have them. Then we can help better.

You need to tell us whether you have a battery switch. And how it is wired.

My 311 did not come with a battery switch. The port battery was wired directly to the port trim pumps and the port starter. The stbd battery was wired directly to the stbd trim pumps and starter. The bilge pump auto switch was wired directly to the port battery. The stereo memory wire was directly to the stbd battery. Both batteries "fed" the distribution panels, and the alternators were wired through an isolator which charged both batteries.

When I added a switch, I left the hardwired things like they were, but I did move the starter wiring to the panel feeds and split the battery feeds to the switch.

That way I could always start both motors off of whichever battery was hot.

I never had a "mean" stereo in it, so I would just switch off one battery at anchor and run fridge and stereo off of one. Even if I ran it dead, I could swap to the other battery, start the motors, and charge the dead one.

If I had a "mean" stereo I would have left it rigged the same way, EXCEPT I would have added one more battery to the side I usually ran at anchor. I still would have shut off the starter battery at anchor, but would have had 2 batts worth of juice to run off of.

MC