Great Lakes Special gas tank size

[beckoning]

How many gallons is the below-deck gas tank? About 5 years ago, I put a new floor in my '88 Sea Nymph GLS 19.5. I remember the aluminum gas tank being at least 15 gallons, but could be something in the 20 gallon range. I cannot find specs on that boat. Anyone know the answer?

 

[ziggy]

look by the fuel sender on the tank itself. it may have a placard w/ capacity of the fuel tank. mine does, and it's a '75.
short of that. run it out of fuel. or close to out, then fill it up. that's how big yer fuel tank is.