THE ACFT EXPERIENCED A POWER LOSS ON ONE ENGINE DURING TAKE-OFF INITIAL CLIMB. THE PILOT REGAINED CONTROL OF THE ACFT AND CONTINUED TO FLY THE LANDING PATTERN. ON THE DOWNWIND LEG THE ENGINES RAN INTERMITTENTLY. TURNING FINAL BOTH ENGINESSTOPPED. A FORCED LANDING WAS MADE IN AN OPEN PASTURE 1500 FEET SHORT OF THE RUNWAY. THE PILOT STATED THAT HE REFUELED BY THE TIME FLOWN AND FIGURED 15 GALLONS OF FUEL AN HOUR AS AN AVERAGE CONSUMPTION. ON THIS FLIGHT HE WAS GOING ONCE AROUND THE PATTERN. HE ESTIMATED THE MAIN TANKS TO HAVE 7 GALLONS EACH. WHEN ASKED HOW HE ARRIVED AT THAT ESTIMATE HE SAID 'WHEN HE LOOKED INTO THE MAIN TANKS HE WANTED TO SEE 7 GALLONS AND THATS WHAT HE SAW.' DURING THE FORCED LANDING THE LANDING GEAR WAS DAMAGED AND THE ACFT COLLIDED WITH A TREE WHICH SEPARATED A WING. BOTH OCCUPANTS RECEIVED MINOR INJURIES. AFTER THE ACCIDENT THE MAIN TANKS CONTAINED LESS THAN A PINT OF FUEL. THE AUX. TANKS CONTAINED ONE GALLON EACHTHE TANK SELECTOR WAS POSITIONED TO THE MAIN TANKS. THE PILOT SAID HE HAD PLANNED TO REFUEL AFTER THIS FLIGHT.