Try to get a siphon hose right to the bottom of the tank, either through the filler, or the gauge sender hole if it has one, I used a garden hose with a Snapper lead taped on, move the boat to get the hose to the lowest point and siphon fuel out, no amount of miracle cures will get all the crap out, regardless of what you are told, or what the label says, siphon from the bottom is a must, drain it into plastic tanks on the ground.