I/m wanting to change the distributor in my boat. It's a 5.7 with the mercruiser thunderbolt ignition. The distributor I want to go to is a Davis Unified two wire unit. I know one wire goes to ignition hot and the other goes to the tac. My question is how to wire the shift interrupter that cuts the ignition for a split second so you can shift back into neutral. I would think the two wire dizzy is grounded through the body. I've serched the net for others that have attempted this to no avail. 
