1986 Johnson GT 150 runs after key is off

[LiquidCache]

Hey guys, quick question.

I just bought this boat about a month ago, and have run it a few times, and brought it out in the lake once. I have never had this problem before.

I started her up today, to flush it out, and make sure everything is fine before we go out next week. I let her sit and idle for about 3 minutes, then i shut it off, but she wouldn't shut off. The pitch of the idle changes, the idle goes down, but she didn't die. I had to give it gas in neutral for it to die.

I tried it three more times, and the same thing happened.

Any ideas?

 

[tashasdaddy]

Re: 1986 Johnson GT 150 runs after key is off

probable bad ignition switch. unplug the big red plug, at the motor and clean the contacts. it that doesn't do it. look at the ignition switch. it has to be replace with the correct one, or you will blow your electronics.

 

[ezeke]

Re: 1986 Johnson GT 150 runs after key is off

When you turn the ignition key to OFF, the switch completes a circuit between the black ground wire on the ignition switch and the black and yellow wire on the ignition switch; this grounds the powerpack and prevents further firing, stopping the engine instantly.

You need to trace the black and yellow wires running to the powerpacks and fix the loose or broken wire.

Use the ohmmeter to check the wiring and disconnect the battery. Any voltage reaching the powerpack through the black and yellow wire will damage it.

 

[LiquidCache]

Re: 1986 Johnson GT 150 runs after key is off

I will do it in the AM as it's getting dark here and my multimeter is at work.

Do you guys think it could have been dieseling? I'm new to outboards but i've seen cars do it.

 

[ezeke]

Re: 1986 Johnson GT 150 runs after key is off

It could be dieseling, but that is not likely because you can't usually stop a runaway two stroke that is dieseling except by running it out of fuel.

 

[tashasdaddy]

Re: 1986 Johnson GT 150 runs after key is off

a thought, it may just be killing one powerpack, giving it throttle may be flooding it. or a build up of fuel in the other cylinders.

 

[ezeke]

Re: 1986 Johnson GT 150 runs after key is off

The runaway is caused by built-up red hot carbon that continues to fire the fuel. Adding fuel in any manner whatever will just make the runaway worse.

 

[emdsapmgr]

Re: 1986 Johnson GT 150 runs after key is off

I had the same problem. The tone of the engine changed when the key switch was turned to off. One of the packs was bad and it continued running on one pack. Replaced the one pack and it shut off fine after that.