Outboard Motor Fuel Consumption

I plan to commute 8 miles each way every day by boat, and placed a bid in an auction on a runabout with a 50HP Mercury engine, two stroke.
This is a planing hull with a windshield, 5 meters long, and I guess I would not go at full speed, just enough to get in the way of planing and cruising along like it .
The boat comes with a 20L (5 gallon) tank. Would I walk to the gas station with this on a daily basis?

You will probably burn about 6-8 liters per hour, if the key here is that the speed planing hull. planing boats are not a race particularly fuel efficient, a displacement hull is much more effective provided you keep the speed (and more) down. Without seeing the boat or not knowing the condition of the engine, I suppose you will make regular trips to the fuel station. 4-stroke engines are more fuel efficient, and all that wrenching is not essential to reduce the boat's weight will help. Good luck!

10 miles per gallon.