There's a chip in the key; the ECU reads the chip. Have you tried the other key?
Now I did see a failed fuel pump driver in the ECU on one ski; I ran a separated ground for the fuel pump so the ski would start, but that causes a check engine light. The ECU provides the ground to activate the fuel pump. If you don't hear the fuel pump, use a multi meter to see if you have 12 volts on the fuel pump. No voltage at the pump, check the fuse. If you have voltage, use an amp meter to see if there is any current flow in the circuit. If there is no current flow, check the ground wire from the pump to the ECU for continuity. No continuity, fix the broken wire; good continuity, replace the ECU or run a separate ground for the pump. The pump will come on for a brief period of time when you install the key on the D.E.S.S. post. Then the pump will shut down until the ECU sees a crank signal.