at one of the shows someone told me it doesn't hook up to the remote, hence no insert connection. but i can see from the diagram that they were wrong. i'll order the part. i'm surprised the wires don't have to connect to the engine. my old tach did but it was fairly new, made in the 2000's. i'll let you know when i receive it. thanks, ron
brian, i received the part today. i can bring down at your convenience and leave. in no rush if you can't do it in a day. also have other work if possible, waterpump, new plugs, replace carb floats. but the tach hookup is the main priority. water pump was replaced 4 years ago, but i'v only put 6 hours on it since replaced. can't find a place where the plug would go so i imagine it would just hang somewhere. ron
Not to stick my nose where it should not go but, The tach pictured is for a Merc thunderbolt system, it will run off the switch box rather than the stator. This may mean it will run on a double coil if you can get both pulses from the points, not sure, but I doubt it. I run my air guide tach which looks like yours on the 6 cyll with thunderbolt, that boat is still under shrink wrap but about 99 % sure it goes to switch box rather than stator, it would not run on stator hook up. Late model tachs go to stator for sure.
The control you have is 64, 65,66 vintage so, tach wiring does not come up to control, nothing that has a pulse comes up to control with that vintage control/ wire harness. The wiring in the square box is the same as the earlier oval boxes EXCEPT when a 66 has the thunderbolt option but, even then, no plug. In 67 the plug appeared in the control, three wires, ground plus 12v and pulse. Depending on tach, pulse (green) would go to switchbox or to stator. Plus 12 was for light in the face if so equipped. Ground contacts inside control to ground that comes up through main harness.
The easiest way to run a tach on the 2 coil 6's is a tach for a 4 cycle 6 cyll hooked to only one coil, Same number of pulses per rpm. If you want to stay Merc they did make tachs good for the 4 cycle 6's they used on the I/o's when they had points prior to going electronic.
Anyways you are in good hands but may have the wrong tach....I hope I'm the one who is wrong!
I hope that works for you. I am following this thread so I can learn. I am still trying to find out for sure what tach model number I need for a 1965 100 I-6. I need to search and read more, but this caught my eye and is helping to narrow (or eliminate at least). If you end up finding it does not work for you, but would fit mine, perhaps I could buy it from you so you wouldn't be out that money and put it towards the correct one. Just a thought. I will watch and learn more I hope. Where can I read up more on this subject?
The years it will fit are 67 and up. Needs to be thunderbolt ignition after 66.
You can wire direct to motor or plug in to control if it has that provision.
The 65 and 62 Mercs you have are dual coil, same system. i know the 700 is a 62 but make sure of the year on the 1000. Two coils mean 62 through 65', a switchbox single coil thunderbolt could be a one year only 66 style or 67 on
"Vintage Merc" can mean anything prior to the 80's to some!
It's hard now to find a true marine tach for the dual coil systems so go with an auto one set for a
6 cylinder and wire it to ONE of the coils per instructions with tach. i just use one for prop testing I have on clip leads for the earlier motors I run. You can still find vintage thunderbolt ready tachs so it's easier on the later but still vintage motors.
More good information here - so thanks. I am still trying to keep learning and understanding. It looks like I may be resorting to finding a newer tach and/or also marine mechanic help. I was really wanting to use the vintage Airguide tachs and just read more and study diagrams until I was sure I had what I needed, but I am not there yet. Since my Merc 1000 (100hp) is a 1965 I-6 with dual coil and distributor...and my controls do not have that front wiring plug configuration, I am still searching further. One chart is leading me to believe I need the 655 rather than a 666 (which I believe is for the Thunderbolt ignition motors '67 and newer). Any further help on letting me know if I am on the right track would be appreciated. If I could for sure find the right model number and wiring diagram, then I would do it...(or if I had someone tell me how to make the newer 666 model work with the 1965 dual coil motor,,,if that is even possible, then I would do that). I apologize that I am no expert, but I am trying to learn more and stay within my limits until I do so. Thanks!
I just need to keep reading, researching, and learning...because not only do I not want to burn up any electrical on the tach OR the motor, I also do not want to burn up a powerhead by over-reving a motor. I have boated enough in 50 years to know my prop pitch is a bit too small and seems like it will surpass recommended redline...but NEED the tach to dial in the best pitch for my rig. If I learn anything that is in written form, I will share it. I cannot afford to just "wing-it". Sure would be nice for both of us to find an original rig with the same equipment (which HAS a tach)sitting at the next gathering and find out for sure what model works.
Whatsleft - Thank you for that link. I was there once, but lost the link. I read through that one time and guessed at a 666 model and bought it. Well - I was both hasty and wrong. Thanks you, I just got off that link after reading further...I finally had to take a leap of faith and pay for a download of a wiring diagram of another model that looked closer...but I still was not sure...after reading the words and wiring diagram, it just might be the 665 that works for me. I will read it more. It still didn't actually say the year "1965" I6 merc...I do not want to pay to download several models just yet. I will check my Merc manual and look at my motor to determine if it is correct. It does also say the 665 has that module to go with the gauge. It also states that the factory matched the same serial number on both the module and gauge to ensure they work accurately together. Ok - my head hurts for the night. I will try to look at it with fresh eyes over the weekend.