capacitors
 

I see a lot of people that install them but don't know if they are a must in a stereo system. I am running a kicker 850.4 and a boston acoustics gt50 for amps running WS threesome six boston 6x9 and a boston 10'' sub. Is a capacitor a must in this system and is there a difference in the $40 ones of of ebay compared to the $140 ones at car toys?

A capacitor is basically a battery that releases it's charge all at once. In my opininion on a boat, where the batteries are very close to the amps usually, it's not necessary. You might se a slight increase in the strength of the bass when it hits a peak, but other than that it's pretty unnoticable. The thought is that they deliver a quick shot of juice to the amp when it demands it.

my batteries are in the back of the boat and the amps are up front under the dash

My batteries are in the back too. I have 2 amps in the front storage locker with 4 gauge wires running from the batts to each amp. I don't know if I needed it, but I installed a 1 farad cap next to each amp. It seemed to help, but to be honest, I also tuned my amps correctly at the same time, so who knows. Either way, it's not going to hurt it.

All a capacitor does is capture electricity and store it for a short time, like Bawshogg said. Then it releases the electricity all at once giving a powerful blast to whatever you are trying to electrify. Stun guns are a good example of how capacitors work. They run on simple 9v batteries, which are not painful to get shocked by. However, they contain a capacitor that gathers that energy from the battery and stores it because it has more "capacity" to do so. Then it unleashes it all at once when the trigger is pulled and you get the painful stun instead of an annoying shock. The only reason you would need one then, is if you are trying to get more power to your amps than the battery can supply on its own... That is.. if the battery is the weak link in your sound system go for it, but if it aint broke don't fix it.

another thing to consider is that capacitors aren't 100% effecient.... in other words if you are using one they are going to be using power also and will degrade the total runtime of your system