My rectifier tested bad at the shop. The guy had a used one for $20 so I bought it. I bid on one online so I will have a spare. So I put it on and have tested while running the motor. 12.85v at 1200 RPM at the the rectifier and 12.65v at the battery, 12v at the fish finder on the dash. Tach still didn't work so I ran a jumper from the tach to the terminal on the rect. Still nothing. I switched to the other terminal and it worked. So I moved the gray wire over and have a tach now. Why is this? Only half the rectifier working? Maiden voyage Saturday with the Merc. on the boat. Can't wait! 