Unfortunately the boat is in storage so I cant give you model numbers but both are Kenwood.
Amps are grounded at the capacitor (8 gauge) which is grounded at the battery (4 gauge).
I know Im wired correctly. The sound system can wake up people in another state (and its crystal clear with NO distortion). Even when its turned up (and the boat is off) it has to get pretty loud before I can have something cut out.

After doing some research on the internet I ordered a blue top Optima marine battery (class 31) last night...1125 amps which is double what I have now.

Now the next question: right now I run 3 battery's. (1) for starting and (2) for the stereo...Presently all 3 are Die Hards but now that Im adding the Optima do I need the additional Die Hard (not sure if its a good idea to run a 500 amp and a 1125 amp battery in series...or should I have 2 Optima's OR just (1) Optima for the stereo and (1) Die Hard for starting?

You can run two optimas and a die hard, but would use a battery isolator. If your amps are cutting out when cranked up while the engine is running, it shouldn't be the batterys causing a issue. Depending on how far your amps are from the batteries, you may not need the capaciters. I never used them and have had multiple big amps running with never any issues.

How old are the batteries in the boat now? You can put a volt meter on them to see what the voltage is coming out of them. Capacitors may actaully be hurting you in this situation more then they are helping. They are designed to run at 14 volts so the recarge could be slower. I will try and call my buddy at AMP and find out what is up with that. You may want to think about some small solar panels that you can toss on the deck when listening to tunes to keep the thing running.

Best bet would be to load test all your batteries and see how many amps they can provide. If they fail their specs on the load test, replace them. I have seen batteris show 12.5V, but fail the load test. Your starting battery might be good, but you may have a bad stereo battery. Also, standard starting batteries are not designed to be discharged and recharged like when running a stereo while at the beach for hours. Get deep cycle batteries for that.

Powerquest - I have the same exact problem on my 25 Outlaw. I have four 10" JL subs and eight 7.7" JL component speakers. I am running two 1000 watt PPI amps. I know I am wired correctly to and my ohm loads are matched to the amps. I have tried several things. First I had my amps in the cuddy with 4 gauge wire to each amp (a pos and neg from the battery to each amp for a total of four cables) and it cut out when I cranked it up. I then moved the amps from the cuddy to the rear bench seat. This shortened the power cables to about 5 feet each, still same problem.

I noticed that if I turn the bass down (almost off) it didn’t cut out as much, but who wants to do that? A boat without heart pounding bass is just another boat!

I am running two Blue Top Optimas and I think they are junk. I do not recommend the Blue Optima’s in my option. I have talked to 100 people and have 200 solutions, you know how that goes. I hear ya on the generator idea, great concept but not for me.

I have no idea what to do. I thought about adding more batteries. I was thinking about two banks of three batteries. Yes that’s six batteries, plus two more to run the boat. I had a friend of mine do this and so far it has fixed his problems. He also went with car batteries because after a ton of research he felt that the car batteries take a faster charge and released more power faster (more on demand juice). He discovered (in his option from research) that the deep cycles are designed to have a small but steady load (draw). The car batteries on the other had act the opposite.

I wish I had a better answer but I think we are in the same problem. I think I spent $225 on each of my blue tops and I regret it.

Wanna sell those Blue Tops?, LOL!, in all seriousness EVERYONE has an opinion, kind of silly question, BUT, have you talked to an Audio Expert?, there are several high end audio installers/retailers that deal with marine configurations, if kids out there can run a gazzilion watts of power through 30 Subwoofers in a Honda Prelude, you shouldn't need a half dozen batteries to run your current system?, just my thoughts!

Michael

The stereo ROCKS when the engine is running (ear bleeding) and gets loud when the engine is off but just not to the level I can get it to when the engine is running (but still very loud). EVERYTHING is in the back of the boat--Amps, capacitors and obviously the batteries so my power and ground wires are short (which is good).

Current Die Hard batteries (which are in the boat now) are 2 years old.

The reason it is shutting down, is not enough current, its either the batteries or the wiring, since it is OK when the engine is running, I would say the wiring is OK. Just buy 2 of the biggest batteries(current wise) you can find and be done with it, if your running 2 year old die hards, you need new batteries anyway.

Hay man, I am not trying to put the blue tops down, I think they are a little over priced but they are good batteries they are just not working in my application.

Yes I have asked / talked to a lot of high end guys both marine and auto and like I said everyone has three suggestions. I am with Powerquest, it has to be the batteries because mine is good when the engine running but the freakin engine is loud as heck too. (that’s a good thing!) but on the sandbar, the marina, or floating it cuts in and out at high volume. I have even tried different amps and still the same problem. Do you have any idea how irritating it is to have a couple grand in a stereo and have to listen to a $10 Wal-Mart boom-box with a 9 volt battery? lol!!

So what are the best battery to use for marine / boat stereos that draw a lot of juice? Dose any one have any EXPERIENCE with this or had it happen to them?

No Worries!, I AM actually looking for a pair of Optima's, and yes, they aint cheap!, its just a thought, but, how about yanking the batteries out of either a buddies boat, or maybe even your tow vehicle?, be a bit of a pain in the arse, BUT, it would be A LOT worse to go out and drop a bunch of coin on 2,4, or 6 new batteries and find out that WASN'T the problem. I also agree with an earlier post, get the batteries load tested, you can use a volt gauge to check the batteries, but, you really need to use a load tester to see if they are any good, I too have seen batteries read WELL over 12 volts on a volt gauge that weren't any good.

Instead of a generator?, if you haven't already?, how about shore power, or at least a good healthy on board battery charger, at least then when your in a marina or anywhere near power you could plug the boat in and have tunes without worrying about the batteries going flat.

Good Luck!
Michael