Baja is a good boat, a 25-27' can pull a tube ok if there is room.
80mph single boat is going to average about 2miles per gallon if you are lucky. Twin 80mph boat may get 1.2-1.5 mpg.
For river work a single may suit you better up to 29' from there you will want twins
I'd suggest a single engined factory powered boat for your first go round.