Mercruiser 120 will not shut off constant 12v to coil

[fredcombs]

Hello all. Wanted to present a situation here and looking for a little guidance and if I’m on the right track. 1985 mercruiser 120 on a houseboat (not there currently to troubleshoot) went to start it up a few weeks ago and my ignition coil was cracked and was spewing oil everywhere and the coil was so hot I could not touch it for a few hours. It would also not turn off when I turned the key off. Broke out my multimeter and with the new coil on I am receiving 11.9 volts at the coil with the key off. Tested the key switch and it was bad so I unhooked everything from the back of the key switch and there is still 11.9 volts at the coil. My current thinking is I either have a back feed somewhere or I have a hot wire touching a post it shouldn’t. I disconnected the battery since we were leaving the boat and will tackle it this weekend Any tips on how to diagnose and where to start would be very helpful and much appreciated. Last thing I want to do is throw parts at it without troubleshooting first

 

[Scott Danforth]

start troubleshooting the wiring. there is not much to the wiring on a points ignition 2.5 liter

 

[Bt Doctur]

disconnect the orange output wire at the back of the alt .If this power is gone the alt is backfeeding

 

[kenny nunez]

Look at the starter solenoid, the purple/black wire is contacting the main battery cable or the inside of the solenoid is causing the back feed.
Disconnect the purple/black and check the voltage at the coil. This will prove out the back feed.