Outer Limits 4x4 Board

Hi there I’m just getting back into the 4wd scene after going missing for almost a two years.
I’ve just purchased a 91 maverick lwb 4.2 carby, 5speed manual. in stock condition.
Now heres my problem. I filled up a full tank of petrol and I’ve only done 80km and my fuel gauge it already down to half a tank.It said full when it was full. And I know I should be getting a lot more than that. So I’m wondering what I should be expecting out of a tank.
Also if anyone else has experienced this problem and ways to fix it.

Possibly it could be a faulty sender unit. Fill your tank back up and see just how much you've used. Or its outta tune and needs a bit of a go over. Or the right foots havin some fun with the new toy!.. cheers.

Thanks for the advice, had a feeling it could be the sender.

Could some give me an idea of what i should be getting out of a tank?