New ignition sensor has a ground wire?

[witchy woman]

Hopefully this is a quick and easy question. Mercruiser 5.7 sterndrive, original engine was '99 305, but this engine replaced that a few years ago. Everything off the original engine went on this one including the Thunderbolt ignition. I put on a new distributor cap, rotor and gasket, but while I was in there, I pulled the sensor and it looked kind of rough, so I replaced it as well. Old one (original '99) had only the red/white and green/white wires. This one, from Sierra also has a black wire with a ring terminal on the end. A ground wire, I'm guessing.

I haven't tried to start the boat, ran out of time this evening, but will try it tomorrow. My question is, does that sensor need to be hooked to ground or something else?

 

[alldodge]

Yes, new ones have the additional ground wire, better design. Just find a spot to fasten it to

 

[Bondo]

Yes, new ones have the additional ground wire, better design. Just find a spot to fasten it to

Ayuh,..... There should be an unused black wire comin' outa the harness right by the distributor,.....

It's a pain, but I usually put a little screw in a hole in the bottom of the distributor body to firmly ground it,.....
You could piggyback the new one to it,..... or just use it for the one ya need,.....
The distributor has ground, I just figure more is better,.....

 

[witchy woman]

Thanks men. I've seen that "stray" ground wire in the harness and always wondered what it was for. Now I know.

 

[muc]

MerCruiser is very specific about this wire going to a “good” ground.
MerCruiser is also very specific about what is a “good” ground.
The two ground studs on your flywheel cover are the only places that MerCruiser considers to be a good ground.