On May 20, 2017, at 1615 eastern daylight time, N126MC, an amphibious Maule M-7-235C airplane, sustained substantial damage during a forced landing to a field after a total loss of engine power near Colton, New York. The private pilot and the commercial pilot sustained minor injuries. The airplane was registered to and operated by the private pilot as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed and no flight plan was filed for the flight that originated from Tupper Lake, New York, about 1530, and was destined for Potsdam Municipal Airport (PTD), Potsdam, New York. The private pilot, who had recently purchased the airplane from the commercial pilot, stated that he was at the controls and the airplane was in a right bank at an altitude of 2,500 ft mean sea level (msl), when the engine "coughed and quit." The commercial pilot, who was seated in the right seat and had more experience flying the airplane, advanced the throttle and turned on the boost pump, while the private pilot leveled the airplane and looked for a place to land. The commercial pilot told the private pilot to switch the fuel selector from the right main tank to both tanks. The private pilot stated they were unable to re-start the engine and the commercial pilot, who took control of the airplane, made a gear-up, forced landing to a field, resulting in substantial damage to both floats, the wing struts, both wings, the fuselage, and the firewall. The commercial pilot said there was about 5-7 gallons of fuel in the right main tank when they entered a 30° bank turn to the right. When they were about 6-7 seconds into the turn, the engine sputtered, lost full power, and they were unable to re-start the engine. Initially, he thought the private pilot may have inadvertently placed the fuel selector valve to the "off" position, which inhibited them from re-starting the engine. However, postaccident examination of the airplane revealed that the fuel selector valve was in the "both" position. According to the manufacturer, if a pilot makes an uncoordinated turn, it is possible to unport fuel away from the lines that carry fuel to the engine. The chances of this occurring would increase with less fuel in the tank. The commercial pilot said that this had happened to him before when first he owned the airplane, but he was able to re-start the engine. He said the engine "definitely died due to fuel starvation" from fuel unporting in the wing during the turn. A postaccident examination revealed the fuel selector moved freely to each detent. The fuel line at the outlet of the engine driven fuel pump was removed and no fuel was found in the line. The fuel lines were also removed at the throttle body and the flow divider and no fuel was observed. The electric fuel boost pump was turned on and it was observed trying to pump the small amount of fuel left in the outlet line going to the engine driven fuel pump. No mechanical deficiencies were noted with the fuel system that would have precluded normal operation at the time of the power loss. The aircraft was equipped with a JPI 700 engine analyzer, which recorded exhaust gas temperature (EGT), cylinder head temperature (CHT), and battery voltage. The unit recorded data at an interval of once every 6 seconds. A review of the taxi and takeoff portion of the flight, before the engine lost all power, did not indicate any anomalies with the engine or electrical system. The private pilot held a private pilot certificate with ratings for airplane single-engine land, single-engine sea, and instrument airplane. His last third-class Federal Aviation Administration (FAA) medical was issued on February 16, 2016. The private pilot reported 1,000 total flight hours, of which, 51 hours were in the same make and model as the accident airplane. The commercial pilot held a commercial pilot certificate with ratings for airplane single-engine land, single-engine sea, multiengine airplane with an instrument airplane. He was also a certified flight instructor for single and multiengine airplane. The commercial pilot's last FAA third-class medical was issued on June 4, 2015. He reported 3,375 total flight hours, of which, 1,785 hours were in the same make and model as the accident airplane. The private pilot reported the weather as clear skies with light and variable wind.