Fixing A Old Merc Fuel Tank ?

[framedtrash]

my boat came with a big 75ltr plastic fuel tank when i first bought it

we had problems with the tank which we put down to the connection on the fuel tank its one of the old merc styles that looks like a big T only problem is you cant just unscrew it and put a new one on

just wondering is it possible to change these some how

i rather get the old one fixed then shell out $300 for a new one

cheers