Small Engines (Lawn Mowers, etc.): Exmark electrical problem, safety interlock, electrical problem

Question

Wiring diagram I  have an Exmark Lazer Z with a 25 Kohler Command 25 HP with an electrical problem.  My brother connected the wrong wires to the battery.  There are 2 wires that are supposed to connect to the negative  terminal along with the ground terminal wire.  He connected them these 2 wires to the positive terminal.  Of course, the engine won’t start now.  I’ve checked the battery with a volt meter and it is still ok so I don’t think the problem is with the battery.  I’ve also checked the 2 fuses.  Any ideas?  I've attached the wiring diagram and circled the 2 wires. Thanks

Answer
Does the engine turn over when you try to start it?  If so, do you have spark?  What does the safety interlock module look like?  Are there any part numbers on the safety interlock module.
Let me know.  Can you send me the mower model and serial number?
Eric