Not sure exactly... my boat is very similar to yours and I was told it will hold 175 gallons. I have not had the intestinal fortitude to fill it up. 50 gallons puts the gauge above between 1/4 and 1/2..
I have a 1989 WA2200 and it has a 120 gal tank on it. Open all the access holes in the deck and look at the data plate on the tank....that's where I found the info on mine.
