Sorry to hear about your Gas tank Helmut,I know 1st hand what you're going through,I owned an '89 19 ft Bayliner with the same problem,I'm thinking this boat of yours is a centre console,if so the tank is right under where your chair is,I'd thought about cutting away the console and floor as its fiberglass,but opted to order a 20 gallon plastic tank and installed it under the seat in front of the console,and fastened it down with 2" web straps,and routed the fuel line under the floor and down the right side to the motor-3/8"fuel line.A pic would have helped us visualize where the tank actually is.(20 gal. tank is around $500-strapping is nickel and dime stuff)Oh mine was a trophy model-some trophy! Good Luck Thump