On June 12, 1993, about 0930 eastern daylight time, a homebuilt Rans S-12, N162JT, registered to Trevor A. Sayer, experienced an in-flight loss of control and crashed into a pond at the Massey Ranch Airpark, New Smyrna Beach, Florida, while on a 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The airplane was substantially damaged and the private pilot was not injured. The flight originated about 5 minutes earlier. The pilot stated that while climbing at an altitude of about 400 feet above ground level during a third takeoff, he observed that the exhaust gas temperature gage for one of the two cylinders was indicating higher than normal. He further stated that he observed this during the previous two takeoffs. He turned crosswind but the engine then failed. During a turn to land downwind, the airplane stalled and entered a spin. He partially recovered from the spin but the airplane crashed into a pond and sank. The airplane was recovered for further examination. According to the owner/pilot, the reason for the loss of engine power was due to fuel starvation. This was caused by improper placement of a "Y" fitting which connects the fore and aft fuel withdrawals from each fuel tank. The "Y" fitting was placed in the center of the inboard portion of the fuel tank near the bottom of the tank. Review of the fuel system line routings instructions for the airplane revealed that the fore and aft fuel withdrawals should be "Run a line through the rib grommet, down "A" frame to fuel mixer block." There is no mention of the placement of the "Y" fitting, but according to the designer, if the fore and aft fuel lines are installed as directed, the "Y" fitting will be in the correct position. The pilot included a diagram of the suggested routing of the fuel lines which is actually what the assembly instructions call for.