Recommended gauge wire..

for wiring in 2 amps, sub and tower speakers. Amp for speakers will be running 2 channels at 340 watts @ 4 ohms. Sub amp will be mono @500 watts @ 2 ohms. Is 8 gauge sufficient for both. Thanks.

How long is the run? You could run 4AWG to a distribution block close to the amps then a short run of 8AWG to the amps.

Not quite sure of the exact length of the run. It will be installed in a Supra 21v. Control head is at the driver and so will the preamp. Battery is mounted on passenger side so and that's where the amps will be mounted. Guessing at least 16'. Just a guess since the boat hasn't been delivered yet.

If your amps are going to be mounted on the passenger side and that's where the batteries are located, I can't imagine that it'll be 16' long (unless the battery is in the back and the amps are near the bow). The location of your head unit and preamp have nothing to do with the power run to the amps. Just be concerned about the distance from the battery to the amps. As for wire gauge, it's really based on how many amps the amplifiers are pulling and the wire length. The following link will give you a good guide based on RMS power. From the sound of it, you'll probably want to go with at least 4 gauge. Hope this helps.

http://www.the12volt.com/info/recwirsz.asp

You're right Michael. Amps will be mounted by the batteries. I'm pretty sad when it comes to electrical installations and I can not afford to fry anything. Thanks for the link.