13.6 volts to both sides of the coil with key on

by Bill
(Mica, WA)

Have a 1987 4 cylinder 165 horsepower Mercruiser with an aftermarket electronic ignition. I am getting 13.6 volts to both sides of the coil with the key on. What is the problem and is there a way with a voltmeter to test the electronic ignition module?