If it has still has oil injection turn the key on and remove the motor mounted oil tank cap and you should start getting an intermittent beep. Find the brown wire going to the starboard cylinder head, ground that wire at the wire buss terminal right above the starter solenoid and you should get a solid tone alarm. The horn could be bad or not connected. Most have the horn inside of the shift - throttle control.
“The world will not be destroyed by those who do evil, but by those who watch them without doing anything” GOD IS GOOD