How to: 1968 Merc 650 Tach

[Glassparman]

Greetings, any of you smart guys know how to hook up a tachometer to a 1968 Merc 650 4cyl?

And if so, what tachs can I look for? I've scoured around ebay but I need to know what I'm looking for.

thanks in advance.

 

[usskydvr]

Re: How to: 1968 Merc 650 Tach

Any standard 6K RPM O/B tach will work. Do you have the standard MerControl with the tach connector on the front ( it is about 1" in dia with 3 blade type connectors)?

 

[Glassparman]

Re: How to: 1968 Merc 650 Tach

usskydvr, I have what appears to be the standard control but I just went and looked, there is no connector on the front. I found a wiring diagram on the net that shows the connector but it is absent from my control.

Do you think it is an older control?

Ok so I have been looking on ebay for tachs . . . what the heck is 8 pole, 12 pole and all that???

 

[Glassparman]

Re: How to: 1968 Merc 650 Tach

Hey gang, still looking for help here.

I'm not familiar with all this 8 pole, 12 pole and such. What does that mean and what do I need for my 1968 650?

Also, my control does not have the connector on the front for the tach, anyone know how to hook one up??

thanks in advance,
Michael

 

[usskydvr]

Re: How to: 1968 Merc 650 Tach

The pole number is how many poles are on the stator 12 for Mercury. Some of the earlier controls didn't have the tach connector. You will have to run three wires from the engine to the tach. One for Gnd, one for 12v and one for the tach signal. The switchbox on your ening should have three wires on one side that go to the Dist. There should be 4 terminals on the other side
Green, Brown, Red, White and a black ground that goes to the coil assembly. (the green also goes to the coil) Connect your tach signal to the Brown , connect the 12v wire to the White ( this will have 12v only when the ignition sw is turned on) and the Gnd to the Black.

 

[Gomer50]

Re: How to: 1968 Merc 650 Tach

I have replaced my Tach on my 72 merc 800 with one from ebay but the kicker was the tach did not work when connected to the brown on the switchbox I had to hook it up to one of the Stator wires ( works Perfect)
12 pole Tach.

 

[Gomer50]

Re: How to: 1968 Merc 650 Tach

UNIVERSAL 12 POLE BOAT TACHOMETER GAUGE marine

http://cgi.ebay.com/ebaymotors/UNIV...5175513QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

 

[Gomer50]

R

R

This is the one I use..

 

[Glassparman]

Re: How to: 1968 Merc 650 Tach

Thanks everyone for the AWESOME information, I'm new to the Merc stuff.

So, if i have a tach from a boat that had a 6 cyl Mercruiser and that tach has the little wire on the back to select between 4,6, and 8, will it handle the 12 pole outboard?

michael

 

[Gomer50]

Re: How to: 1968 Merc 650 Tach

No I dont think so, If I am not mistaken those kind are just like cars have.It needs to have the 12 pole setting.The 4,6,8, are designed for 4 stroke engines not 2 strokes

 

[usskydvr]

Re: How to: 1968 Merc 650 Tach

Gomer50 is correct, that tach won't work.

 

[Glassparman]

Re: How to: 1968 Merc 650 Tach

OK, you have all been real helpful but now I feel like an idiot for not doing more research before bothering everyone.

I was told when I bought this motor that it was a '68.

In fact it is a 1966 650 serial number 1898782.

I have been looking at a NOS Airguide Tach at oldboatgauges.com and it says that the model years it starts on is a '67 SS model. Do you think this is because it has the harness that plugs into the front of the remote control? I know that my remote control does not have the plug on the front.

I was hoping it would work anyway using the instructions that usskydvr explained above. The reason I want to go with that tach is that it perfectly matches the design of my Airguide spedo

Again, thanks for all your help in my stupidity!

Michael

 

[usskydvr]

Re: How to: 1968 Merc 650 Tach

The Airguide tach shoud work fine.

 

[merc850]

Re: How to: 1968 Merc 650 Tach

I checked out that tach and it looks like it is designed for Thunderbolt ignition, if your engine is a '66 you will have to use an alternator driven model 12 pole like Gomer50 said.

 

[Glassparman]

Re: How to: 1968 Merc 650 Tach

I knew you guys would have the answer! Thanks for all your help.

I'm working on two different boats. So I'm really crawling this forum for help.

So, can I hook up the 12-pole tach the way that usskydvr stated above?

 

[usskydvr]

Re: How to: 1968 Merc 650 Tach

Yes, If you have the switchbox like I described.