Fastech Stereo System Wiring??
 

This one goes out to everybody that has done some aftermarket modifications to "liven" up their formulas sound system.
A big thanks ahead of time to anybody with suggestions

I have a '97 312 formula fastech with twin 454's and will be doing some stereo upgrades this winter (in combo with dash/instrument panel upgrades). 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 the amps are hooked up to 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?

You should not have a hum even if the engines are running. Couple things to look for.

1) Bad grounds. Make sure ALL the grounds for the stereo system are as close to one another on the boat as possible. If you know how to measure the resisstance in ground then test it you will probably see a difference. I try and run a good size (12 ga or so ground) from the head unit to the amp. Then I use a larger wire (8ga or larger depending on amp size) back to the battery. Make sure the terminals are all clean.

2) If after that you still have the noice check your RCA's. Try not to have them be long so that you have to coil up the extra. The coil can craete and antenna and pull in noise that way. If you can don't run your RCA's with the power wires and so on of the boat. Try and keep them as far from the power wires as you can. Make sure your RCA's are 100% sheilded and of decent quality. You don't have to go crazy but don't go super cheap either.

3) IF after that you still have the noise some times it can be a bad alternator or bad component in the boat some place. Try running one motor and see if you have the noice then shut that one down and start the other. That is the type of trouble shooting that you need to do tell you find the culprit.

Good luck and if you have any other questions just ask.

Jon