Where does the tach get it's reading on a 1988 60hp mercury outboard. Would like to replace the tach. Tach doesn't fall back to zero, stops about 1300 when you turn it off. Also readings are pretty steady at 2000-3000 and 4000 but starts bouncing bad at aound 5000. Have moderate repair skills. Is this something I could do. Thanks

The tach on your Merc picks up it's signal from the grey wire in the harness. the wires on the tach are purple which is key-on 12 volts, black for the ground, GREY is the tach signal wire coming from the rectifier and there may be a blue wire if the tach is lighted. the tach should zero only when the key switch has been turned to the ON position. it is a real simple job to replace the tach. make sure the key switch is in the off position or just unhook the battery. you will need a 3/8 or 11/32 nut driver to remove the bracket as well as the wire connections on the back of the tach. I hope this will help Good Luck

p.s. how bad is the tach bouncing once you reach 5000 rpms? could it just be the rough ride bouncing the needle?

My tach does the same thing, how did you fix yours.