Range Question in 20ft master angler

[Florida85]

Hey Guys,

I am trying to find out my range so I can figure out where I can fish/troll and get back safely. I have an 1982 20ft master angler fish with 200hp yamaha offshore series.

I believe I am the 3rd owner. I asked previous owner whom I bought boat from about gas tank and they do not know if its original. Its hard for me to know the size since I constantly fill it up.

Is there an easy way I could find out what size tank is? Or is there a safe guess on what my range would be? I read somewhere that the standard original tank was 42 gallons.

Please let me know your thoughts.

Thanks,

Justin