Mercruiser 140 coil problem

[danvillemarine]

I am reposting this topic to see if there are any more ideas. This is a 1978 mercruiser 140 4 cyl. Not sure what exact coil to put on it. It was brought to me with a 6V coil on it. Should the new coil have the resistor inside plus external resistor. Or coil w/o resistor and put one on the outside. The coil has two tan wires that come off the + pos side on coil. One tan runs into wiring harness and splices into a white wire. The problem we have is that the wire gets very warm to the touch when key is on and points closed I believe, but will not melt. Normal? I would think most of them should hook up the same way as other years. Just need a starting place.

 

[bruceb58]

Re: Mercruiser 140 coil problem

That warm wire is most likely the resistance wire. If so, it is normal to be warm.<br /><br />To make sure what type of coil you have, take the wires off one of the sides and measure the resistance across the two terminals. You should measure around 1 ohm if is an external resistor coil or around 3 or so if it is an external type.

 

[danvillemarine]

Re: Mercruiser 140 coil problem

I know that the coil we have on their now is a coil w/o resistor. Is that wire going to act as a resistor or do we need to place one. Also I read that it should match up to the points etc. we have. Is it possible to have 1. coil w/o resistor and have the wire warm or 2. coil with internal resistor. Do they act the same.

 

[searay3]

Re: Mercruiser 140 coil problem

Measure the voltage on the positive side of the coil with the key on points open. If it reads battery voltage, you will need a coil with the internal resistor. If the voltage is approx 7, the wire is the resistor. Then you need the coil with no resistor.

 

[danvillemarine]

Re: Mercruiser 140 coil problem

Thanks everyone...I believe the fix is an internal coil b/c we have 12 V with points open.