Manatee gas tank

[Photogx]

I have a 1985 Manatee 17' center console that had a built in fuel tank, it must have leaked at one time and a tank was installed above deck in the stern portion of the boat. I would like to remove, replace or fill the old tank with floatation. I would like hull plans to make this repair easier. Any ideas out there?
Thanks

 

[evildocrsx]

Re: Manatee gas tank

Cut 1 inch holes through the deck and fill the void with liquid foam. I don't really think I know what you are talking about. Maybe pictures would help.