TOPIC: Will my tach work?

Will the tach I have been using on my '63 Merc 850 work on my '77 Merc 1150?
Bill

If on the 850 the tach was connected at the rectifier to one of the yellow wires coming off the stator, yes it'll work if you connect to the 1150's rectifier in the same manner.

If the 850 tach's sensor wire was connected to either one of the ign coils, then it won't work.

HTH.........ed

I doubt it..but I have an airguide that I bought for my 62 700 that will .
Its for thunderbolt ignition that I bought in error. You can have it for what I paid for it off ebay.its real nice. Ron

Thanks for all of the info on the tach and wiring Ed. Ron, I will keep that in mind. I will let you know if I need it.
This is such a great site and everyone is so willing to share their knowledge. I couldn't imagine working on stuff like this before the internet and places like this.
Bill

Ron,
It looks like I might be in the market for that tach. The one I have is hooked up to the coil on my 850, so it won't work on my 1150. Let me know the price and we can go from there.
Thanks,
Bill

I got the tach from Ron today and I just want to make sure I hook it up correctly. It has one green wire and one black wire, with a screw in the center that looks like it may have had a wire (ground?) attached. It is an Airguide tach, if that matters.
Thanks,
Bill

All Dunn II, I am in the same situation you are in with trying to get a tach to work with the thunderbolt ignition. Please post exactly how you hook it up to get the tach to work and what model tach your using,when you get it working. I have a wide variety of tachs and I can't seem to get any of them to work properly.

The tach I have is an Airguide model 666. It has only 2 wires, one green and one black. I hooked the green wire to the stator wire on the rectifier and the black wire to the ground on the engine.
When I turn the engine over it pins the tach past 7 grand. Is that normal? I haven't started it yet with the tach hooked up to see if it works right. I thought I had better find out first, before I fry something.
Thanks,
Bill

Don't believe that's the type of tach that works with a rectifier; according to an application chart I found, the "666" tach is only for Capacitor-Discharge ignitions, 4 & 6-cylinder.

Being that specific, it would have to be connected to the brown terminal on the switchbox (on the side opposite the distributor connections).

If the switchbox on your 1150 has that brown terminal, then it should drive the "666" tach.

According to the Airguide wiring diagram, the green wire is tach sensing, so it should connect to the brown terminal; the black wire goes to ground.

Attached is the Airguide tachs .pdf file, HTH.......ed

Thanks Ed. I will give that a try and let you know how it goes.
Bill

I tried it green to trigger and black to ground. As soon as I turned it over I could see that the needle wanted to go down. I reversed the wires (black to the brown terminal and green to ground) and it works fine. Just thought I would pass on the info.
Bill

Bill, that was convention back in the day. Green was often ground (like the grass) and black was Hot, Blue is often used for Hot as well.
FYI, black wires are only ground wires when coupled with a red wire in a 12 v system, and only when negative ground.

That is one thing that is great about this site - everyone is more than happy to pass on what they know.
Thanks,
Bill