I have a 2001 Islander 292 with twin 350's and dual batteries. I want to add a couple of subs and replace the stock clarion's with some good speakers with amps to power this sufficiently. Question is how much power can I add without a) adding a battery and b) upgrading alternators? or do I need to worry about it? Thanks for all replies.

You should be good if you keep it to 2 or less good amps. I would suggest getting a mono digital amp for the subs because it will draw less power and is more effecient. If you see any power drain when at large volumes you may have to add a capacitor but you should be fine.

Good luck!

Thanks for the reply. What maximum power would you go for?

I'm running a PPI 600 watt 2 channel pushing the two 12" PPI subs under the rear bench and a PPI 200 watt 4 channel running a set of MB Quart seperates and Pioneer 3 ways. I have two deep cycle marine batteries running through an isolator switch so I don't kill both batteries while I'm chillin bumpin the jams at full blast all day!

This is my 3rd system in this boat (Due to theft ) I've run all sorts of different configurations but this one seems to work the best. Buy quality stuff and you'll be happy.

Tank

I've got a Kicker DX700 (digital 700 watts at 2 ohm) for the subs and a Kicker 4x55 for the cockpits 4 speakers. My Sony CDX-MP70 powers the two cabin speakers just fine. My criteria was to have extremely clean sound that I could hear at full throttle and I get it with no problem.

You don't necessarily need "marine" speaker or amps unless you plan on getting them wet... so just keep that in mind. Also keep in mind to have good ventilation wherever you place the amps because that can and will get hot if you crank it.

Good luck!

Tank - question about your subs. How hard was it to mount them under the rear seat. I've seen pics and stuff of some but never really knew how hard it is to do. Do you just cut the holes in it and slap the subs in?

The only difference between marine amplifiers and non marine is that the circuit boards are conformal coated to prevent oxidation. The coating is available from electronic supply houses and a 16 oz can can do about 10 amplfiers. 99% of the time it is not needed, but I spec this as part my design to insure that the product goes beyond its warranty period.
My thoughts on capacitors.... Stiffening caps can and do improve sound quality on amplifiers that have power supplies that are non regulated.These pwm (pulse width modulated) supplies are input voltage sensitive and as the input voltage drops sound quality depreciates. Inversly the more power that is available the better the sound quality.The capacitor is there to provide that extra voltage when the input voltage drops in the power supply. My thought is why spend extra money for a cap...just buy a better amp with a big supply in it. Better grade amplifiers have regulated supplies and as long as your input voltage is at 12v or more they produce full power. When an alternator see a discharged capacitor it sees it as a dead short and can cause damage to the alternator. The better quality caps have a protection circuit in them to prevent damaging the alternator.
Marine Speakers are generally housed with a non metalic basket. The stamped steel baskets are painted or powdered coated but has a tendancy for the finish to wear off and leave rust stains. The steel has less tendancy to flex and generally has better sound quality and a lower price.

thats my .02 worth

When too much is not enough, more is better, and excessive is just right!

97BossHammer

Here is mine 2 10" Kickers under the rear seat. This is a 25 Outlaw though. It was a piece of cake, I had someone do it for me. Really I watched them do it, its pretty simple.

Another of the boxes they built on the back of them.

I dont have boxes built in for my 12's. The first set I bought were a set of Kicker free airs. They sounded AWESOME!! Then I had some JL W2's, They didn't work as good. Now I have the PPI's. they are adiquit but I would really like to get free airs again. I just let the seat act as the box. It is not hard to install at all and I did it myself. Just cut the holes and slap 'em in. If you're going to go with the box. That gets tricky.

Tank