66 100hp can I add a tach?

I recently removed a working tach from a 1967 650 with I believe a type III ignition. The tack was factory wired with a plug and pigtail from the control box to the tach. I would like to put the tach on a 1966 100hp with the two automotive style coils. Can anyone tell me how to wire it in? Thanks

The 66 -100 hp is a wonderfully simple motor.------It should only have one coil !----------The tachometer that you need is driven by the alternator and you need the correct one for the the big powerhouse alternator found on the 100 hp.

Which motor have you got? This one http://www.maxrules.com/oldmercs/Wiring/0_1965a/8.pdf or this one,http://www.maxrules.com/oldmercs/Wiring/1966ona/32.jpg .If it's the first one.....I have no idea,possibly take the brown wire from the back of the tach to a yellow wire on the rectifier.
If it's the second motor,and you still have the same controls,there is a brown wire that hooks to a brown terminal on the switch-box,and this is the wiring diagram for the back of the tach.If there is and orange module on the tach,unlikely as it came off a 650,remove it.I have the actual installation destructios somewhere but as I changed the computer a week or so ago I'm having bother finding it,when I do and if you need it I'll post it

I just reread your post and I see it is the first one.I'm not trying to direct you away from this forum,but the folk at John's Old Mercs will be able to help
http://www.johnsoldmercurysite.com/phpBB3/viewforum.php?f=7

Assuming it has an alternator, most people use these windings for the tach signal (and "6P" for the tach input. Just grab one of the yellow wires from the stator for the tach input.

Jeff

Utfyrfytr says he going to use an old,working tach and there's no adjusting pole on it,and I'm wondering if the controls from the 650/65hp are being used.If not,a sig output wire will need to be run from the rectifier to the tach and a ground found and if a light is needed a connection to a 12v+ as well

I deleted this post

Thanks for your help and efforts. I am not using the 650/65 control box. I can find a ground and a 12V positive lead I just don't know where to pick up a signal for the tach. The old 1000/100 is a points and condenser breaker style and I believe the 650/65 is a pointless ignition system. I think finding where to locate a signal is my only issue.

There should be two yellow wires,possibly with a red stripe, coming from under the flywheel.Follow them to where they terminate,it should be at a block with three poles,the two yellow wire and a red.Attach a wire,brown or grey to either of the yellow wire pole and run it to the tach,that will be your signal wire.The colour choice is yours,but it was usually brown on older Mercury outboards and grey on the newer.I only give the colour as the marine industry has a standard colour for a particular use these days. http://www.marinemechanic.com/site/page101.html

Thanks, you have bee a great help.