I know this is going to sound convoluted, but I will do my best to explain. I have a 1996 Mercruiser 4.3 Gen+ mated to an Alpha One drive. I don't have any serial #'s handy. The ignition is what I believe to be Thunderbolt V, it has the ignition module mounted on the rear of the distributor and no knock sensor. The engine was a supposed reman installed in the spring of last year, due to a freeze and bust.
I bought the boat last fall at a discount and knew when purchased it had/has a shifting issue. The boat is hard to get from forward to neutral on the water and will skip from reverse straight to forward most of the time. At the time of purchase I assumed it to be a bad lower shift cable, which did not bother me.
I had the bellows, gimbal bearing, etc. done this spring as well as a new lower shift cable installed. Mechanic says shift cable is installed and adjusted correctly and my issue is something electrical (which is an area he doesn't know much about). After some investigation I found the green/white wire coming from the shift interrupt switch to be unhooked as well as 3 wires from the ignition module (2 green/white's and a red and white). I assume these wires were to go to the ignition sensor mounted within the distributor (red/w & gr/white) and the other green/white to the shift interrupt switch. All of the other wires coming from the module were connected and appear to be right compared to a wiring diagram.
Upon further investigation I found what appears to be another ignition module mounted on the transom of the boat. It has gray, purple, wh/red & wh/green wire(s). The gray and purple were going to the - and + on the coil respectively and the red/wh and green/white wires were connected to the ignition sensor that is inside the distributor.
When I unhooked the ignition module mounted on the transom from the ignition sensor, and hooked up the wires that were removed from the other ignition module the boat started and seemed to run fine and the shift interrupt switch worked properly, but the boat will only run until it gets up to operating temperature and then it shuts off, like the ignition has been grounded out. It will then restart and die again until it cools down.
I have 12v at the coil with the key on, I have 12v from the red and white wire coming from the module with the key on. Unhooking the tach and unhooking the shift interrupt switch seems to make no difference. I know it isn't fuel because the boat runs perfect with the other module hooked up, but there is no wire coming from the module to hook up the shift switch. I ran a jumper from the shift switch to the - side of the coil and it will stall the engine when the switch is manually depressed, but for some reason will not work as it should on the water.
Is the module mounted on the distributor bad and has someone installed the other module in an attempt to bypass it? If I can use the module that does not have the wire for the shift switch to hook into, how do I wire the shift switch where it will work correctly. I hope this isn't too confusing and I appreciate any advice or help. Thanks