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Engine will not turn off when key is turned to off position

J

Jay Martin

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I have an 85HP Force OB that

I have an 85HP Force OB that will not turn off. I installed a new ignition switch with the same results so I don't think that is the issue. I was told to check the ground wire. I did and even performed a continuity check. Everything appears to be fine. Is there anything else I can check or some way to "short/bypas" the ground to determine where a short might exist?

Does the ignition switch need to be grounded?

I have a Prestolite ignition.
 
"Jay,

If you look on the te

"Jay,

If you look on the terminal strip on the port side of the engine, you will find two black-yellowstripe wires which lead to the CD units.

These are the wires which are grounded when you turn the switch to the off position, and thereby shut down the engine.

Be very careful when you do this. Start the engine, and take a length of wire or a test lead. Touch one end to the black-yellow stripe wires, and the other end to ground. The engine should turn off when you do this. If it does not, then the problem is with these two wires or the CD units themselves. If it does turn off, then the problem is somewhere between the ignition switch and the terminal strip on the engine. I believe the wire that connects to the terminal where the black-yellow wires are connectd is white, but it could be any color. This wire must lead from the terminal strip to one of the "common" terminals on the switch. The other "common" terminal must be grounded. Both of these terminals on the switch are generally labeled "M". That is the entire shut off circuit.

"
 
" Jay,

Hopefully some

" Jay,

Hopefully someone else will swing by to tell you exactly how that works, but here's my .02, it should help. On my mercury, the ignition is killed by grounding out a specific terminal on the black boxes. In line with this terminal are: the MOB kill switch (puts ground to circuit when yanked), ignition switch (in off position it puts ground to this circuit) and a "mercury" switch, which grounds out the circuit when the engine is trimmed up (and never works). When the key/MOB/"mercury" switch are in the "on" position there is simply nothing connected to this circuit.

I have no idea about force, but assuming it's similar: Yes, somehow the ignition switch needs to be grounded in order to kill the engine, else there would be no way for it to ground out the ignition. In addition, it's probably not a short, but a lack of a short.

So, my advice would be to first try using the MOB switch; if that works the problem is just your key switch isn't grounded; if that doesn't work, the problem is either the entire control box needs a ground, or that the something along the line is not making contact.

Good luck, keep in mind that I'm making the assumption this is similar to a merc.

Jon "
 
" Tony,

Didn't m

" Tony,

Didn't mean to repeat; we must have been posting at the same time.

Jon "
 
I have a white wire that is l

I have a white wire that is listed as Magneto. I also have a blue wire that is listed as Magneto. Do both of these need to be connected to the same "M" post?
 
" Jay,

The white wire shoul

" Jay,

The white wire should be the grounding out wire which conects to the black-yellow wires. These wires may be white also, depending on the year the CD modules were manufactured.

The blue wire is designated as "stop 2", and usually is not used, the white wire being connected to both CD modules, however, you have to be careful here. Sometimes, over the years, wires can get connectd improperly, or are used for some other purpose. What wire(s) does the blue wire connect with at the terminal strip?
Sometimes this wire is used as the grounding wire for the "m" terminal (which is being used as ground)on the ignition switch.


Feel free to join in, Jon; the more the merrier.

Tony "
 
"Jay,

After looking through

"Jay,

After looking through a number of circuit diagrams, I am unsure about exactly which ignition system you have. There are a few different configurations used and the wiring is slightly different for each.

If you could give me the year and/or model number I could probably zero in on the exact schematic for your engine.

Tony"
 
I don't know the year. F

I don't know the year. Force started using the Prestolite ignition system in 1983 so I'm guessing it's a mid-80s engine.
 
" Jay,

Does the engine have

" Jay,

Does the engine have a distributor, and does the distributor have breaker points?

Tony "
 
" Jay,

I thought that was t

" Jay,

I thought that was the case; this would make the engine no older than 1984 and not newer than 1989, with a Type III ignition system.

They did make CD ignition systems with both breaker and breakerless distributors, and the circuitry for them is different that what you have.

So, we can go back to Sept.17, 9:42 am, and take it from there. The white wire from the harness should connect to the black-yellow stripe wires (which might be white), which ground out the CD units. This white wire in the harness must lead to one of the "M" terminals on the ignition switch. The other "M" terminal on the switch must be grounded. This can be done through the blue wire that you mentioned if it is not being used for something else. I noticed that on some schematics this wire is used for accessory power of some sort. This is why I asked about what wire it connects to on the terminal strip. The danger is that it might be a hot lead, and connecting it to the CD units would be disasterous. Connecting this blue wire to the same "M" terminal on the switch as the white wire would serve no purpose, unless you wanted to ground each wire from the CD unit on a different terminal on the terminal strip.

These engines were sold on a number of new boats throughout the 80's. On some, the source of ground for the grounded "M" terminal was somewhere under the dash, so the blue wire could be used for another purpose. On others, the blue wire was used as the source of ground. It would connect to a grounding wire on the terminal strip on the engine.

On the earlier ignition systems, the blue wire had other functions, depending on the type of distributor.

I hope this helps.

If you are not totally confused yet, I can try a little harder next time.

Tony "
 
" Thank you all for being so h

" Thank you all for being so helpful! I am still trying to figure this out.

Tony,

I have a blue wire (labeled magneto). It is not connected to the switch but it comes back to the engine and connects to the wiring harness. It has a "jumper" to the black wire connection. So it looks like it's connected the same as the black wire. Now, on a wiring diagram I have, it shows the blue wire connected to the "M" post and not the black wire. I don't know if this makes a difference because it worked when the black wire was connected.

My white wire feeds into the harness and out the other side, two white wires feed into the CD units. Can I ground the white wire at the motor to test the ground?

BTW, I can post pics to a web site if needed.

Thanks again all! I'm hoping I can get this thing going by this Sunday - the kids are going nuts! "
 
"Jay,
You can post pics right

"Jay,
You can post pics right here on the board...

The instructions are in the "Formatting" section on the left. If you have any trouble you can email them to me and I will post them here.
Regards,
Andrew
"
 
" BTW, I just got off the phon

" BTW, I just got off the phone with Mercury. They said the moter is a 1988. "
 
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