Tach for '68 Merc 500SS

[seaking1]

How do I wire up a new Teleflex tach for my 1968 Merc 500 SS with Thunderbolt ignition? <br /><br />Teleflex said their tachs will work with series 2 or newer Thunderbolt systems and not with series 1 systems. Although I have the original owners manual as well as the Mercury service manual I'm unable to determine which series I have. I spoke with Mercury last week and they were not able to help me; in fact the "old timers" said they never heard reference made to different series Thunderbolt systems.<br /><br />I have the three-lead tach wiring harness with white (instrument light), brown, and black wires. <br /><br />Anyone know how to identify the ignition systems series and/or how to wire up the tach?<br /><br />Thanks!

 

[RobG]

Re: Tach for '68 Merc 500SS

seaking1,<br /><br />This website should help you with the wiring diagram, I have a '68 Merc 500 that I am rewiring.<br /><br />Thanks<br /><br />Rob<br /><br /> http://www.maxrules.com/wireindex.html

 

[seaking1]

Re: Tach for '68 Merc 500SS

Rob,<br /><br />Thanks for the link. I have the Mercury service manual that includes the wiring diagram. I also have the original owner's manual that has the diagrams for both the 500SS and the 500S. Do you happen to have the service manual?<br /><br />The manual indicates that each motor uses a different tach which are wired up differently. From what I recall, the original tach was wired up similar to the picture in the manual. Unfortunately I rebuilt the dash two years ago and didn't save the old tach so I have nothing to reference. <br /><br />Which motor do you have, the 500S or 500SS? Have you installed a tach? Also, do you have any idea on how to identify which series Thunderbolt ignition system you have?<br /><br />Thanks for your help!<br /><br />seaking1d (AKA Dan)

 

[ricksrster]

Re: Tach for '68 Merc 500SS

Tachs work by pulses from the charging stator. Hook your send wire to either yellow or yellow/red post on the rectifier. Do not hook to ignition. Set the switch on the back of the tach to 6P. Hook a wire from the ignition switch on to ign on tach. ground on ground and run a wire from toyr lights to the light post on the tach.