voltage at coil

[Thumbtack]

I have a mercruiser standard ignition (points) with a coil that is getting extremely hot. With ignition on i have 12.5 volts at the battery and about 10.5 volts at positive wire at coil, i would expect it to be around 9 volts with the resistor wire, is this 10.5 too much?
If this is a problem do they make a coil that doesn't need a resistor, or do they make a resistor i could put inline with the wire?

 

[Chris1956]

Re: voltage at coil

Thumb, The voltage is already lower at the coil, than the battery. Why do you want to lower it further? The lower voltage helps protect the points from burning, but degrades the spark.

You can get a ballast resister or a coil with a built in resistor. The questions is does your ignition system have the correct components in it now? if so, why do you wnat to change them out?

 

[JustJason]

Re: voltage at coil

are you leaving the key on when the engine is not running? if so, that's a no no with points.

 

[gdombroski]

Re: voltage at coil

Coils are made to operate a 12 volts. The resistor is to lower it to protect points. May be time to replace coil.

 

[Thumbtack]

Re: voltage at coil

Thanks for the replies, i replaced the coil and everything seems fiie now. I don't leave the ignition on when the engiie isn't running because i know that would burn the points. The coil was getting super hot to touch when engine was running. And the reason i was wondering about the resistor is because i know someone was playing around down there. But i thought the voltage at the coil was to be at 9volts but i guess not.
Thanks agaii

 

[JustJason]

Re: voltage at coil

if you wanted to double check, and you still have the old coil. sand off some of the paint on the coil houseing and put your meter on resistance. Check for resistance between the primary, secondary, and the high tension out to the coil housing, it should read infinity. If it does not then you have a coil thats shorted internally..... (may or may not work, it's possible for the coil to past the test when cold, but fail when hot)