Twin Johnson Ignition Grounding

[Incorrigible]

I have two years work into my latest project and am now working on sea trials. The boat is a center console powered by twin 1990 Johnson 225hp

The ignition keys are mounted into a OMC bezel that has three cutouts: One for each key and one for the kill switch.

The issue is this: I cannot run one engine without having BOTH keys in the "ON" position. Is there any way to wire the ignition switches so that I can move the key to the "OFF" position on one engine and still run the other?

What happens is that by turning off one key, the "M" terminal grounds, and through the SINGLE kill switch, this grounds the second ignition switch.

??????

Thanks!

PS: It's been forever since I've posted here, but over the last two years I've been a regular reader. EXCELLENT source of information from some very well-learned individuals.

 

[jonesg]

Re: Twin Johnson Ignition Grounding

I would seperate the systems, run a second kill switch.
As it stands now, if you get stray voltage into the black/yellow kill wire it will blow all powerpacks out on both engines.
I'd probably run seperate batteries too.

 

[Incorrigible]

Re: Twin Johnson Ignition Grounding

The kill switch is to ground, not to the powerpack so that resolves that one.

I've done a bit more researching and it turns out that the reason I have the problem is that the ground terminal on either ignition switch, once grounded, back feeds through the kill switch (even when it's open) and grounds the terminal on the other kill switch.

What Johnson did to resolve this issue was to put a diode in one of the kill switch terminals. Unfortunately, that diode wasn't there when I went to reinstall the kill switch....

 

[Incorrigible]

Re: Twin Johnson Ignition Grounding

Oh, yeah. Almost forgot.

I am running separate batteries (actually, three of them)