1978 Evinrude 85hp V4 won't shut off

[MadtownChris]

Hi folks. I've got a 1978 Evinrude 85hp V4 that won't shut off when the key is turned off or removed.

The problem was intermittent until recently and now it seems to be happening all the time.

I saw some related posts but those seemed for older models in which the wiring is different. I also could not find the right wiring diagram for the engine and year in the top secret files: https://maxrules.com/JOwireindex.html

It has 2 power packs one of which I replaced about 6 years ago.

Where should I get started for diagnosing this? I have a multimeter which seems like step #1 but I don't know which wires to test for what.

Thanks!

 

[racerone]

With key in the ---run----position the 2 " M " terminals should show open.---With the key in ---off----position the 2 " M " terminals should show closed.

 

[MadtownChris]

The key switch is working as you describe. What's next to check? Thanks

 

[oldboat1]

You probably have a black going to one of the M terminals and a blk/yel stripe going to the other. Trace the black one to make sure it remains grounded (two grounds I believe, one in the vicinity of a CDI module).

 

[MadtownChris]

The black wire coming out of the ignition switch wires is firmly attached to the engine block. I did not check the continuity of the wire itself from the key switch to the engine block.

But if I understand what you've said and the wiring diagram here: https://maxrules.com/graphics/omc/wiring/80_81_V4.jpg when the key is off the yellow+black wire should form a circuit to ground. When the key switch is on that wire is detached from ground.

In the pics you can see I pulled the connector where the yellow+black wire goes in and checked whether that wire had a connection to ground (engine block) with the key off and on. On both sides the yellow+black wire formed a circuit to the block with the key off and no circuit with the key on. I checked a couple of times since the problem is intermittent.

I should note that I'm 90% sure the whole motor runs when the key is shut off - it doesn't seem like the left or right side shuts off and the other keeps running - there's no difference in sound.

Where should I go from here?

 

[oldboat1]

Seem to be on the same page -- but I think I've run out of pages. Continuity tests of the wires, as you mention, would be a good idea. I would think key switch but sounds like you checked that. It doesn't seem likely that both power packs would fail, but perhaps both depend on a single ground.

 

[MadtownChris]

The wire diagram doesn't seem to indicate any dependencies between the power packs. Maybe my monkeying around with the throttle and key switch put it back in working order for a while. I'll have to see if it's still occurring. It probably will never happen running my driveway and only while on the water.

 

[CarMech1969]

In the pics you can see I pulled the connector where the yellow+black wire goes in and checked whether that wire had a connection to ground (engine block) with the key off and on. On both sides the yellow+black wire formed a circuit to the block with the key off and no circuit with the key on. I checked a couple of times since the problem is intermittent.

Like oldboat1 said, you want to be sure that the black wire running from the key switch to the engine ground has a constant ground. If there is an intermittent connection along that wire, it will cause the condition you describe.
You could conduct a "wiggle test" on that wire as you are checking for continuity to ground to see if ground is lost.
What happens if you use the kill switch (the button with the red lanyard attached to it) to try to stop the motor?