25 merc wont run if battery is connected

[wenied]

Ok guys..here's an update.. (figured i'd start a new thread since this is a new problem)
I cut off the dead rectifier...cleaned the carb...dumped my fuel and got fresh fuel..added the oil and some sta-bil....cleaned the fuel filter.....then pulled the rope.
Motor started on the first pull.. I let it run for 20 minutes or so.

I then hooked up the battery....cranked the motor...it would not start(turns the motor fine..just wont fire).. I pulled the rope..it still will not start...

I disconnected the battery and it starts on the first pull.

So now the motor runs fine but will only start if the battery is disconnected....i tried both of my batteries..they both have a full charge....

HELP!!!

 

[JUSTINTIME]

Re: 25 merc wont run if battery is connected

sounds like your key switch is bad or emergency stop switch on your control box is bad maybe?

 

[tashasdaddy]

Re: 25 merc wont run if battery is connected

that was my 1 st thought, but wouldn't the kill switch work without the battery installed. and the engine would not start if the key is not in the on postion, even without the battery.

 

[wenied]

Re: 25 merc wont run if battery is connected

that was my 1 st thought, but wouldn't the kill switch work without the battery installed. and the engine would not start if the key is not in the on postion, even without the battery.

Exactly!...the key has to be on for it to run...even with the battery disconnected. The kill switch works properly too.
Any ideas are welcome as this has got me confused and frustrated.

 

[Silvertip]

Re: 25 merc wont run if battery is connected

Obviously the engine runs without the battery and the battery is used only to energize the starter and run accessories. Somehow battery voltage is influencing the ignition system so I would start by looking at the wiring on the ignition switch.

 

[tashasdaddy]

Re: 25 merc wont run if battery is connected

confused me too.

 

[ricksrster]

Re: 25 merc wont run if battery is connected

start at the battery. Red = POS, Black = NEG. Follow these cables to solenoid and ground. check wires from ignition switch and harness. check the wires in the engine harness. Looks like you have a wire grounding out.