Where to tap into a 12v source for electronic points and new coil

[Justinweigt]

Good Afternoon,
This weekend I am going to get rid of my points in my 1974 Mercruiser 3.0. I know I have to tap into a 12v source for the new coil. Where should I do this? Starter, Solenoid or alternator? I have pictures, I added at the end of the post. Currently I have two tan wires running to the positive terminal of the coil. Do I just remove them and not use them again or does one wire go somewhere else? The wire diagrams on the internet do not really show what I'm looking for. I am hoping you can help.

Thank you,

 

[Bt Doctur]

None of those places. It must be a switched 12v source. If you have an electric choke you could get 12v from there.
Personally I would keep the points. Not that hard to service.

 

[Justinweigt]

I do not have an electric choke.
Any other ideas

 

[stonyloam]

You should be able to add a fuel pump relay to provide voltage directly from the battery. Activate the relay with your current ignition wire going to the coil +, and pick up 12v from the hot side of the slave solenoid, or starter. That is how I run my Petronix, that way I am assuring full voltage to the module and coil. Mine is bolted on with one of the valve cover bolts.

 

[Justinweigt]

Can I just tap into the ign. wire in the bundle of wires?

 

[Bt Doctur]

Ypu would have to open the wrapping just after the main plug and locate a purple wire.

 

[Justinweigt]

thank you

 

[stonyloam]

You should have a resistance wire going to the coil +. It should only be 18 inches or so long, so just trace it back to its end and you can get your 12v there.

 

[Justinweigt]

Thank you

 

[Justinweigt]

Does a resistance wire have any markings on it or is it just a color?

 

[stonyloam]

According to the "old" wiring diagram, you should have 3 wires on the coil +. Tan to the starter solenoid, a white to the alternator a an another ( maybe white) resistance wire.

 

[Justinweigt]

I only have two tan on the coil, no white

 

[jaa241]

Has the pertronix unit change anything for you? Have you got connected up? Just wanted to check in, have been away sorry.

 

[Justinweigt]

Yes, it runs smoother, very easy to install. I tapped into the purple ignition wire. Tested my old resistance wire and it was bad.