Mercruiser 120 Coil and Resistance With Points

[lognum]

Cheers Forum Mentors. Looking for some guidance and hopefully a resolution. I see a lot of the same issues with coils posted here, but never a viable solution. Hoping this time around, there may be one. I have a merc 120 stern drive serial number A635702. The system is points. What reading should I have at the positive of the coil when running? Coil does not have an internal resistance. Using the resistance wire currently. Cheers

 

[matt167]

Coil needs to have resistance. If it reads 0 ohm something wrong. 1.5 ohm is what you need.. ohm measured across the terminals with ignition off

 

[lognum]

Coil needs to have resistance. If it reads 0 ohm something wrong. 1.5 ohm is what you need.. ohm measured across the terminals with ignition off

Thanks Matt. What voltage reading should it be on the coil positive post when running? Cheers

 

[matt167]

Thanks Matt. What voltage reading should it be on the coil positive post when running? Cheers

Same as off. It’s a resistance wire so it’ll be under 12v. It should be at least 6v iirc. That won’t tell you much tbh. A test light is accurate enough to verify the circuit for spark

 

[lognum]

Same as off. It’s a resistance wire so it’ll be under 12v. It should be at least 6v iirc. That won’t tell you much tbh. A test light is accurate enough to verify the circuit for spark

Thanks again Matt. One last question; what replacement coil would you recommend, part number/s ? Engine is 4cyl 1985-86. Cheers

 

[matt167]

Thanks again Matt. One last question; what replacement coil would you recommend, part number/s ? Engine is 4cyl 1985-86. Cheers

Oddly enough you can go to Napa and ask for a coil for a 1965 Chevy II with 153 cid 4cyl and you will get the right one

 

[lognum]

Oddly enough you can go to Napa and ask for a coil for a 1965 Chevy II with 153 cid 4cyl and you will get the right one

Appreciate the advice and assistance! Enjoy your evening. Kind regards