I have a Force 50hp 2stroke (1992) and a new set of gauges. The tach appeared to be wired correctly by a boat shop, but it doesn't work. I removed the Faria tach to hold it closer to the motor figuring everything would be direct to the gauge and there wouldn't be any shorts. I wired positive, ground and then the grey wire from the rectifier. The pulse for Faria was set to '5'. Nothing happened. I switched to all the different choices of pulse settings and none of them gave a reaction. Can I try the purple wire (hanging by itself)?