Originally Posted by efiste
According to the wire sizing chart I referenced, #4 wire can only support up to 100 amps over a short distance and the negative should not be more than 1 size smaller than the positive.
Neg return and pos should always be the same size or no sense in having one larger than the other. DC circuits are loops so all wire should be the same size. It is the CASE GROUND of the inverter than can't be any smaller than one size below the DC wiring. This is a green wire connected between the inverter case and your ships ground/Earth, usually the engine.
The older Catalina wiring was undersized. All the newer Catalina's such as the C309, C310 & C320 uses 1/0 or larger from the factory.
4GA is marginal at best especially when folks start adding batteries and the lengths get longer....