Re: Fuel Tank Cleaning
I just bought a used boat with an internal tank and I was curious the answer to this as well. I found this on another site. It sounds easy, but replacing the tank is a whole other animal. That requires ripping up the floor and replacing the tank and floor again.
First pump out all the old gas, you can use a fuel line and primer bulb to siphon it, works great. Then add a couple of gallons of fresh gas with a fuel system treatment and stabilizer, you can add a water absorbing product at the same time. Mercury makes a great treatment. By using the water absorbing you help get any water out, the fuel treatment will help get any gunk out. Then drain.
If you can take the tank sender out carefully, be sure not to tear the gasket, mark the sender and tank for orientation for reinstallation. Using a wet dry vac hose turn it on blow and blow into the tank with the filler cap undone for at least 5 minutes.
Now look into the tank with a flashlight. If the tank is clean, OK. If not refill with the treatments an fuel and let sit a day or two and try again.
After the tank is clean install a cartridge type water separating fuel filter in line. That should take care of it.
Do this in a well ventilated place. No sparks or open flame anywhere. Dispose of the bad gas at an approved facility.
