Wire gauge on alternator

This has nothing to do with Tacoma's but since I've posted this in a boating forum and haven't gottem any decent responces I figured I'd post here. I have a 1997 Four Winns w/ a 5.7 liter V8 just installed a sub/amp/speakers. The Amp pulls 58 AMP at the MAX. My alternator on the boat was a 65 AMP alternator and it decided the crap out the first day I had the radio. I beefed up the alternator to a 90 AMP alternator but was told I needed to upgrade the wire going to the starter. I took it to a guy who said he was going to install the new alt and put in a new wire. He charged me a a couple of hundred $$ just to install and didn't install the new heavier gauge wire. The current wire on the is an 8 gauge wire. Do you think that is enough or do I really need ot upgrade?

 

http://wiki.xtronics.com/index.php/Wire-Gauge_Ampacity

Go by the alternator's rated output.

 

Sorry that posted before I finished typing.

 

The wire from the battery to the starter is fine.
The wire from the alternator should be upgraded.
The existing 8ga is only good for 73 amps.
New alternator being 90a needs to move up to #6, and I'd seriosuly consider moving to #4.

Don't forget to check/clean/upgrade your ground wires as well. Just as much current is moving through that as through the hot.

 

I kind of figured that I would need to but was hoping to get by with the 8 gauge. Thanks for you help.

 

Rich is dead on with his recommendation for smaller wire gauge. The reason is full load voltage loss due the resistance in the wire over distance. Millivolts and temperature matter when it comes to fully charging a battery. The ability to fully charge the battery and average Depth-of-Discharge affects it's total number of life cycles.

 

Larger wire gauge.... smaller number