200 amps is the typical fuse for a inverter that size. So is #4/0 wire.
Typically the fuse is sized to what the wire can handle without overheating, and also limited by what the manufacture recommends as a maximum size for that model inverter.
So even if using 100 amp rated #4 wire for less voltage drop on a 500 watt inverter only a 50 amp fuse would be installed.
I guess it also matters how many batteries are involved, because if only 4 batteries, then you might consider a smaller fuse, so that the battery will not overheat before the fuse blows when you have a huge load on it.
Read your time manual. It will tell you in the installation area.
Second, Third, Forth, Fith, Sixth, Seventh.
In short, I support this post 100 percent
The answer is in the manual. 300 amp class T
The following is a cut and paste from my Prosine 2.0 manual
DC Cable Length - - - - - Cable Size - Fuse Amps
Less than 6 feet- - - - - - - 250MCM - - - 300A class T
Between 6 and 12 feet - --350MCM - - - 300A class T
NOTE: After a nice chat with Xantrex support back in 2006, I recommend upgrading the cable (Use bigger wire), they recommended taping the neg and pos cables together for as much of the run as possible.
Nothin adds excitment like something that is none of your business
Kenwood TS-2000 housed in a 2005 Damon Intruder 377