40 force engine seams to keep running on one cylinder when you turn key off.

I just purchased a Bass Buggy with a 40 hp Force by Mercury marine. When ever you turn the key switch off to kill the engine it sounds like it continues to run on just one cylinder. Also if you turn the kill switch off while running it does the same thing. I believe the motor is a 1994

Thanks in advance for any help.

Re: 40 force engine seams to keep running on one cylinder when you turn key off.

Are you sure the motor isn't "dieseling" from poor gas? What type of gas and oil mixture are you running?

If the gas is OK, then it sounds like you may have a poor ground connection. Check all of the ground wires that run from the plate that the coils and switchbox/regulator are mounted on to the engine block. Also the negative battery cable where it is attached to the engine block.

There is a black wire with a white stripe that comes off of your switch box. This is your engine kill circuit. With the key off, or the kill switch lanyard disconnected, you should read a short to ground with an OHM meter. With the key in the on position and lanyard attached, it should read open, no continuity.

When you turn the key off, or pull the lanyard, this wire (black/white) gets shorted to ground which kills the ignition system.