Re: Kill switch wiring
About 1988 Merc quit the Tower and redesigned these engines to run on 3 cyl. The last year of the 150 tower would have interfered with the first year of the V6 150 so they stamped it 140 hp.......as I understand the story. I had a 115 tower that was sold to me new in '89 as a '89 model but guys on here said that '88 was the last year they were made. So I guess I had an '88 marketed as a '89. That's the way it's registered in TX. anyway.
With that said, I would assume yours is an early model as they made them for a long time. I don't know when the Optimax 150 first hit the market.
The black with yellow stripe goes to your ignition module to kill triggers. It's in the wiring diagram for the controls. When you turn the key to OFF in on a 2000 or 3000 Commander control (at least) the ignition switch ties that wire to ground thus killing the triggers and the engine.
I'd look at the remote wiring harness inside the engine and see if a black/yellow stripe wire is there. If so, follow it to wherever it goes in the engine. If it goes to your trigger module, use it I'd say because that should work regardless of whether or not your engine is new or old in the series. I don't understand your terminology for early models.
HTH,
Mark
