Coverting 225 Ficht from internal fuel tank to portable external tank

I have a 1999 Evinrude Ficht 225hp outboard which utilizes a 50 gallon built in internal fuel tank. I have major concerns with the fuel system because the boat has seen very little use the last two to three years. Fuel often gets stale and have worries about the Ethanol, etc. Wondering if there is a way to convert to using portable tanks so that I don't have to keep extra fuel sitting unused in the built in tank. Is it even possible to run the big Ficht on a portable tank? I have an oil water separator filter in use but still fear future problems as the gas just does not get used up. Figure if I can install a second set of lines to portable tank I can just remove the tank after use and solve my stale fuel problems/worries. Anybody have any input here?