System check lights off but horn on

[NICKS37777]

I have a 2005 Johnson 50 hp 2 stroke with the system check light and horn. This has been working fine but yesterday the horn sounded constant while running, turned off checked for blockage in water intake but was clear, check oil tank, it was full and primed with pressure in bulb. Turned key on and horn was constant but no lights. Started fine and checked for water discharge which was strong, turned back off and used trolling motor to get back. Today I tried to start it but when I turned key on again no lights but horn was on constant. Did not start it today until I find the problem. Have checked past treads but have not been able to fine this same problem. ( new member ) thanks

 

[racerone]

Maybe the horn itself is defective.

 

[jakedaawg]

Yes, I think maybe a bad horn or temp sensor. Assumes you are not over heating and can rest a hand on top of the head. Is your system check guage a stand alone or integral to the tach?

 

[oldboat1]

What is the surface temperature -- top of the head?

 

[Chris1956]

A Service manual will provide an electrical check on the sensors.

In a nutshell, if you pull the connector off the system check tachometer, you can check the sensor wiring,

Check the tan/yellow, tan, tan/orange and tan/black wires for continuity to ground. Any continuity to ground will set off the alarm.

For 2 cycle motors, these correspond to No oil at OMS pump, Overheat, Fuel restriction and Low oil in reservoir, respectively.