guys what is best way to clean out closed system. want to get rid of any crap, scale, rust etc. over the counter stuff seems lame. thanks

I just picked up some wood bleach from ace for this very reason. Everything I've read said oxalic acid is amazing for cleaning up rust out of a system. That said I've never used it before though so I'm going into this as a newbie.

what exactly are you trying to clean out ? the heat exchanger ends come off to be able to be cleaned, only thing left are hoses, cooler(s) and sea water pump