I had Sea Tow come out and do mine last summer after a number of what I thought were E-10 issues. I could not believe the amount of gunk, water, sludge and particulate that came out of there! You'll need to have access to the senders and a couple of hours to kill. They can either polish (filter) the fuel/tank or dispose of the fuel for a charge. There is also a charge for how many filters they use.