88 force 50 doesn't shut off

[adrock430]

Hi,
I have a 88 force 50 507x8c outboard that I'm trying to get in the water. Starts up fine, runs well, but won't shut off. Shut off fine last year, but now its an issue.

Worked on it this weekend, noticed that the choke bar was a little short, adjusted it, and it turned off fine. Went and put it in the water, then it wouldn't shut off again.

I replaced the ignition switch, and searched through the grounds, and that seems to be fine. There seems to be constant continuity between the two magnetos. Low, but constant. Any specific areas I should be looking into?
Thanks, Adam

 

[adrock430]

Re: 88 force 50 doesn't shut off

Also, where does the ground wire attached to the ignition switch? Does it at all?
Thanks, Adam

 

[Jiggz]

Re: 88 force 50 doesn't shut off

There are two "M" contacts on the ignition switch. One of them is either white or black/yellow which connected to the CDM. This is the stop wire for the CDM which if grounded will stop the engine. This happens when you turn the ignition in the "Stop" position where it connects to another "M" contact with a blue/black or blue wire. The other end of this blue/blk or black wire is connected to ground.

You should also have a separate stop switch which is in parallel with these two "M" contacts.

 

[adrock430]

Re: 88 force 50 doesn't shut off

There are two "M" contacts on the ignition switch. One of them is either white or black/yellow which connected to the CDM. This is the stop wire for the CDM which if grounded will stop the engine. This happens when you turn the ignition in the "Stop" position where it connects to another "M" contact with a blue/black or blue wire. The other end of this blue/blk or black wire is connected to ground.

You should also have a separate stop switch which is in parallel with these two "M" contacts.

View attachment 154508

Thank you for the quick response. That was my understanding of how the switch worked. Should my black ground on the ignition side be in contact with the blue magneto wire on the ignition switch?

The way I have things wired is a white to M, yellow to S, red to Batt, green to Choke, white to the other M, and the black is just sort of hanging out there. The wiring diagram says nothing about the ground on the ignition switch side.
Thanks, Adam

 

[Jiggz]

Re: 88 force 50 doesn't shut off

OK so may it looks like black wire on the other "M" contact but the wiring says it to be blue/black or blue. Anyways, since one "M" contact already has the white wire then the other "M" contact should have a wire that connects to ground. This can be the black wire you are referring to this is the ground wire (other "M" contact) that shuts off the engine.

If this wire is just dangling, get a piece of long wire and locate a ground. or better yet, a wire with alligator clip and attached it to ground. Long enough you can access it from the driver seat. You should now have two dangling wires, the black wire from the ignition sw (if it's not long enough extend it temporarily) and another wire from ground. Ran engine on muffs and then place the stop sw in stop position. If the engine will not stop, connect the two dangling wires. If the engine stop there's your solution to your problem.

You can also just ground the wire before starting the engine if the engine starts and stops, then just permanently connect the black wire to ground. However, since I cannot really see where this black wire is connected to, the first option is safer. We don't want to fry anything.

 

[Jiggz]

Re: 88 force 50 doesn't shut off

If the attached pic is too small to read, make sure you click it again and focus on the top left hand corner which is the ignition sw. Trace the two "M" contacts and you will see where it grounds (actually it traces all the way to the starter solenoid.

 

[adrock430]

Re: 88 force 50 doesn't shut off

Great, thanks Jiggs! I'll give this a shot this week and will follow-up if it works. Thanks again, Adam

 

[Frank Acampora]

Re: 88 force 50 doesn't shut off

88 was not Mercury ignition, it was Prestolite. There will not be a black with yellow tracer.

Stop mechanics are: White wire(s) from the CD box go to the ignition switch. At the switch, with the switch off, they are in continuity with the blue wire which is grounded. This ground discharges the capacitors inside the CD box to ground instead of the coil(s) and no spark is made.

Thus, you must check all connections on white and blue to be certain they have continuity otherwise there will be no grounding and stopping. Check for broken wires too.

OK. On the switch the blue wire goes to one "M" terminal and the white attaches to the other "M" terminal. Black ground is not used BUT can also be attached to the BLUE "M" terminal.

Now, back at the engine terminal board, white connects to white and blue connects to blue. BLUE is jumped by a bar to ground.

If the engine does not stop with the switch off, the two "M" terminals need to be checked for continuity: with the switch OFF they should have continuity or 0 ohms. If they do not, replace the switch. If it is a new switch, exchange it.

By the way: Do not touch the "M" terminals with the engine running unless you like getting a thrill. They have a potential of over 200 volts.

 

[adrock430]

Re: 88 force 50 doesn't shut off

I'm looking at the wiring diagram, and this is a 88 507x8c, says so on the outboard. Thing is, the wiring diagram of prior to 1988 'D' is more accurate. On my outboard, there is no module then coil, the blue and white both become brown and go directly to either one CD or the other.

 

[adrock430]

Re: 88 force 50 doesn't shut off

Also, there is continuity between blue and white when on off, and also when the switch is turned in the on position. Brand new switch.

 

[Jiggz]

Re: 88 force 50 doesn't shut off

You're right the Prior to '88 "D" wiring doesn't have a grounded "M" contact. However, make sure the black wires on each CM-Coil module are attached to ground. I will still try to check if combining the two brown wires together and grounding the blue wire will solve your problem.

 

[adrock430]

Re: 88 force 50 doesn't shut off

Update from this weekends work. A friend an I worked on it, and jumped from the negative terminal on the battery to the blue wire when the key is in the off position. One coil would stop firing, and another wouldn't, so it continued running.

We then did the same thing and disconnected the wires from the plugs to determine which coil was still firing, turns out it was the top one. Any thoughts on what would be causing this?

 

[Jiggz]

Re: 88 force 50 doesn't shut off

Can you try this for me. I've having second thoughts with '88-50HP prior to the "D" model ignition switch. I think instead of the two "M" contacts having continuity in the "off" position, they should instead be opened (or no continuity). To test this can you disconnect one of the brown wires off the terminal board and tape it off to make sure it doesn't touch anything. Try starting the engine, did it start? If it did not, then it tells me the ignition switch when in the off position should have an opened "M" contacts. and will have closed "M" contacts in the on position. Thanks. Don't try touching the brown wires while engine is running, it is charged.

 

[adrock430]

Re: 88 force 50 doesn't shut off

Thanks Jiggz...if it turns out that the off position is open 'M' contacts, and not off, what should be the protocol in finding the error?

 

[Jiggz]

Re: 88 force 50 doesn't shut off

That means it requires a different ignition switch which I have not heard of yet. The standard 6-pole switches we use with the grounding shut off system has continuity on both "M" contacts in the off position and no or open in "ON' position. So where you able to try the above procedure?

 

[jaydoc83]

Re: 88 force 50 doesn't shut off

h a smilar issue with 1983 90hp Chrysler. A temporary or permanet option which I have rigged myslef is : Buy a push choke button switch. Attach white m and black ground to back of switch and use it as a kill switch. In theory it should shut off as I had similar issue. Make sure engine shut of and disconect from battery while applying. You can get a nice jolt form it. For some reason blue magneto in my motor had feedback when the ignition switch went. It got extremely hot when I attempted the blue and black. So beware of that as well.

 

[adrock430]

Re: 88 force 50 doesn't shut off

Jaydoc, your idea did cross my mind, thanks for the tip!

Jiggz, I did what you said. When you disconnect a brown wire at the main bus, it wants to start up, but can't.

I have figured out the problem though. I ASSumed that harness itself was in good condition and that everything was fine from ignition to bus. After checking all the grounds, I decided to recheck. Turns out the white M wire was busted at a hard to see position on the harness. There is continuity between the two M's @ off position, there's continuity between the two until I hit the break, and none thereafter, so it has to be the issue.

I haven't spliced things back together yet, but will confirm when I do...I'm absolutely sure this is the problem. Thanks for all your suggestions!