40 hp 4 stroke EFI warning sig.

[joe43]

I have a 2004 40hp 4stroke EFI merc.. the warning horn starts to beep after about 200 yrds 1/2 to full throttle and continues to beep for about a min then the motor will stop dead. turn the key off and it will start right up it will troll all day and not do it. I replaced the gasket under the thermostat area, and now it does this I disconnected the temp sensor, the oil pressure sensor and it still does it. the I did the crank snsor, the map sensor, the tps and the motor responds but the horn still goes off. I checked all the wires and can't find anything.. any Ideas were to go with this will help thanks

[boats.net]

Need to have it put on computer diagnostic to see what faults are activating.