I have a single engine single battery set up now.What would be the best way to wire in a second battery for stereo upgrade?
Thanks in advance.

The stereo (no matter how extreme) is just another accessory. You need to make sure the wiring for the stereo is adequate and properly tied into the boat's harness. Get yourself a battery switch from your favorite marine retailer. Hook it up according to the instructions. Adding a battery isolator will prevent one battery from discharging the other. It's that easy. When you anchor, use the weakest battery to operate your stereo, etc. and when your'e ready to go, switch over to the stronger one to crank. An added benifit will be the ability to combine both batteries' power to start the motor if you need it.

Perko makes a good dual battery switch for about $20. You can get then at Overton's, Bpater's World, or your local marine store. They are the make before break type which means that it never disconnects power when switching between batteries so you won't lose your radio presets, etc.

Ted...

You will have to wire your constant to one of the batteries as has already been mentioned. If not you will always loose your presets. Other then that fallow the directions on the switch and you will be fine.

if i use one battery to power the audio system when the engine is off, should i switch to dual batteries (both on) when cranking and running as to charge both of them up?

If I run my stereo battery down then I switch to the good battery to start then once both engines are started I switch to both to charge them both. I do not have an issolator so that is the best way to do it. If you have a issolator then you can got both to start. The dead battery take off from the power of the good one if you try and start on both. That is why I go to the good one then switch. I go to both so that it is less strain on the alternators then going to the low battery and charging that one exclusivly on start up. If you go to the dead battery the alternators will charge at full output for a while and that taxes the whoel system.

Jon

its not really a good idea to switch the batteries while its running is it? isn't tht kinda hard on the ecm for injected engines

carburated so i don't have that prob

thanks for the helpful info

I switch my batteries all the time when the engine is running, never had a problem. Since the Perko switch never disconnects the power (unless you switch to off of course), I don't see that it would be a problem.

Ted